#baelon targaryen son of viserys

[nobodysuspectsthebutterfly]

What do you think about Jeyne Arryn's heir? Do you think choosing Joffery Arryn was a mistake, or it's better than Arnold anyway? And If Jeyne was Aemma's niece, why Jeyne didn't choose Rhaenyra, or her children, or her dead brothers as Arryn's heir?

Jeyne chose Joffrey, a cousin who was loyal to her, and who (unlike Arnold) never tried to contest her rule (twice!) just because she was a "soft" woman. I think that's a pretty good choice when you're looking for leadership of all the Vale and its lords and ladies, men and women.

And of course Jeyne, while loyal to Rhaenyra, prioritized an Arryn-named family member, born and raised in the Vale, her Knight of the Bloody Gate and thus experienced with the Vale and Eyrie's people, politics, and defenses, over a distant Targaryen cousin who never set foot in the Vale with no feelings for the Arryns beyond a quarter of Rhaenyra's sigil. Would you ever expect any less from any other ruler?

Also, Rhaenyra's dead brothers? The ones who died 30 years before Jeyne did? Who died when Jeyne was under 10 years old and "ruling" under a regent? Rhaenyra's dead brothers who would have been heir to the Iron Throne if they had lived for more than a few days (which they didn't)? The brothers who were dead? What? *confused-obama.gif*

No, seriously, I am incredibly confused by your understanding of the timeline here. By the time Jeyne died from the Winter Fever in 134 AC, the only descendant of Aemma Arryn known to be alive was Aegon III Targaryen. Who was, you know, the king of Westeros. How was Jeyne supposed to name any of Aemma's other descendants as her heir in her will, reconstruct Rhaenyra* and Baelon** and unnamed** and Joffrey** from their ashes? Pull Jacaerys** and Lucerys*** and Viserys**** out of their watery graves? Seriously, what?

*Rhaenyra was, y'know, the queen, and before that heir to the throne, she wasn't going to be the Arryn heir. **Heir to the throne before he died, so not going to be the Arryn heir. ***Heir to Driftmark before he died, so not going to be the Arryn heir. ****Not actually dead! Even though everyone thought he was when Jeyne was writing her will. But if he hadn't been, he would have been heir to the throne, so still not going to be the Arryn heir.

[gotham-at-nightfall]

Daemon meets Caraxes

By Acker

[midnight--sadness]

i love the way that a dragon's coloring is sometimes connected to its rider's family.

meraxes had silver scales and was ridden by rhaenys. rhaenys' son aenys had a dragon named quicksilver, and though we don't know her coloring, given her name and her pale white fire, it is probably silver as well. aenys' daughter alysanne had silverwing, described as a silvery dragon.

three generations of rulers who had silver she-dragons.

jaehaerys i rode vermithor, the bronze fury, and his son baelon the brave rode vhagar, who was described as bronze.

aemon and alyssa, brother and sister, both rode red dragons, caraxes and meleys, respectively.

rhaenyra has the yellow-gold syrax, and her son lucerys who rides arrax, described as having yellow fire and gold eyes and crest.

(could even connect this to aegon ii's sunfyre, who is golden and has pink membranes, matching to rhaenys' meleys and rhaena's morning, who is fully pink.)

helaena and daeron, also brother and sister, rode dreamfyre and tessarion, both blue dragons (although in different shades).

although we dont know his coloring, stormcloud, based on his name, was probably (dark) grey, which would match with the (light) grey color of seasmoke, who belonged to laenor, aegon iii's stepfather.

and of course, there is the connection between the conquerors' dragons balerion, meraxes and vhagar with dany's children drogon, viserion and rhaegal.

[littlemarse]

to my abo beta!Lucerys thread (old)

[darilarostarg]

My hot take is that if Jaehaerys and Alysanne had any sense they would have betrothed Rhaenys to Visery the moment he was born...

[acewithapencil]

Lucerys meeting his loved ones in the afterlife ❤️🥲

[translannisters]

Look the AO3/Tumblr brain trust did shape my perception of this and I'm not going to pretend it didn't. But also as generally unenthusiastic about Fire & Blood as I am I do think understanding whatever the fuck Baelon and Alyssa had going on is crucial to understanding what the fuck Daemon had going on with regards to his brother and his niece. You are NOT going to get a normal conceptualization of yourself and your family relationships when you grow up being considered the Boy Version of your mother whose relationship with your father seems to have gone down in the popular consciousness as the absolute pinnacle of idealized Targaryen incest. There's a chilling dissonance to F&B's recounting of Alyssa's story not least in that we'll never know how she actually felt about her brother beyond the anecdotes specifically told to justify their arranged marriage - but we have a much better idea of how Daemon felt about his brother and what it led to (and not to extrapolate too much but. I think we also have a decent idea of what it did to Daemon to be unable to fulfill the - horrific - duty prescribed to the mother he took after because of his gender! And certainly of what it did to Viserys to grow up with "sisterwife who happily dies for you in the birthing bed because she can't die for you on the battlefield" as the romantic duty owed to him as his birthright!)

[wolf-saint]

It is truly wondrous what you've built. Oh, no. I only pore over the histories and provide the plans. The stonemasons built the structures. Do you believe that Westeros can be another Valyria, Your Grace? That depends, whether you speak of the Freehold at its height or at its fall. Over a thousand dragons, a navy large enough to span the seas of the world. The glory of Old Valyria will never be seen again.

[maegalkarven]

The "They used to tease me because I was different" genuinely made me laugh bc like.

Aemond...sweetie. You were not different. Your brother was a twat and exposed your insecurities, dragging others into it, but you were NOT different.

Viserys claimed a dragon. (who then died I believe solely from embarrassment bc...Duh. it's Viserys we're talking about)

Rhaenys CLAIMED a dragon. Daemon CLAIMED a dragon. Laena CLAIMED a dragon. Shit, even Helaena ends up CLAIMING a dragon.

And you know what it means???That in their youth they DID NOT have a dragon. They did not have a dragon egg or the egg did not hatch. Aemond, you were NOT different.

And I blame mostly Viserys because how hard was that to explain it to a child?!

[horizon-verizon]

In the book, Aemond seems to have quite an obsession with Daemon. Where do you think it comes from, and how would you interpret/characterize it ?

I’m still thinking about it in ways that aren’t already know or talked about in the current fandom and here on Tumblr. So bear with me here. I might do many edits on this post in the immediate and far futures.

*Update* I was right.

In all and of the two, Daemon acts more out of love than Aemond does, even with him being as violent and brutal as he is. Daemon is flawed and cruel, while Aemond is evil and cruel, though both are ambitious. They both acted out of a lack of love or attentions or recognition at some point.

By and large, Aemond is a character who finds his personhood only through disenfranchising others. He is the potently evil shadow of Daemon. Aemond is a character who lacks love or a true understanding of respect and considers Daemon the beast to slay to solidify and validate his own existence, worthiness, and masculinity.

A)

Aemond is Daemon’s narrative and literary foil. 

A foil is:

a literary device designed to illustrate or reveal information, traits, values, or motivations of one character through the comparison and contrast of another character. A literary foil character serves the purpose of drawing attention to the qualities of another character, frequently the protagonist. This is effective as a means of developing a deeper understanding of a character by emphasizing their strengths and weaknesses. In addition, a literary foil allows writers to create a counterpart for the protagonist that puts their actions and choices in context.

B)

Both

They are both fighters with skill. Both are brutal and willing to get violent (but in different ways and reasons). Both are Targaryens and proud of it. Both want the throne or a strong claim to it. Both are second sons tasked with the role of supporting their older, not-very-competent or completely incompetent brother to keep or gain the throne and are passionate about it (for different reasons). Both squirm with the thought that their existence and purpose is to support such brothers but for different reasons.

And as @theblackqveen says, they even both have a connection to Visenya the Conqueror through her dragon and her sword.

Daemon

1)

Daemon is uncaring of not-family people. Not hateful, just uncaring and thus willing to spill their blood if that will bring him results (Jaime Lannister).  Canonically (not HotD), he is a charismatic, violent, and ambitious man.  He creates the gold cloaks and inspires the preexisting city guardsmen into believing in their own validity and strengths by revamping their looks, etc.

His mother died when he was 3 from labor complications. Unlike Viserys who seemed to have responded to this by being too much a people pleaser, Daemon sought to completely look out for a small set of people he would think of as his family or “close ones”. 

Baelon’s grief would have inspired such reactions from his sons--Viserys to be eager and affectionate, obviously caring. He wants to believe that hospitality and following a sense of duty to those around him will bring him love or contentment. He may have found it difficult not to judge Daemon for taking a “misguided” approach or path, so when Daemon disagrees with him or disobeys his order or does something that is conventionally upsetting, he may have found it difficult to relate to Daemon or see things from his persepctive. While Daemon would, in my mind, is outwardly or superficially crotchety and unwilling to seek/initiate obvious intimacy but needing to be validated through his family and loved ones. However, he doesn’t think words or hugs brings comfort or favorable outcomes--he depends on action. 

So he develops his own moral compass that is just adjusted to “do these people act like I matter to them and do they matter to me” all the fucking time because he comes from a dwindled, fraught lineage (Rhaenys' death in Dorne; Aenys' conflicts and stress with the Faith; the Faith; the conflict with Maegor and threat towards Jaehaerys/Alysanne; the internal issues in Jaehaerys' early reign and Rogar Baratheon; Aemond, Baelon, Alyssa, Viserra, Daella, Daenerys-- nearly all Jaehaerys and Alysanne's children die & Jaehaerys' political focus on the Targ's dominance-survival). That plus he wants to, in some way, bring glory, prosperity, and more power to his house.

Daemon and Viserys would have still received the genuine love of their father, Baelon, and would have grown up together as caring brothers, enough that they would know they loved each other. We have reason to believe that his upbringing was still loving and that he maybe thought himself his brother and father’s caretakers. If not in traditional sense, in that he is the one who will do “what it takes” to keep them afloat. In his mind. Especially after his father passes form a “burst belly”, leaving him and Viserys alone. Seeing how Viserys is so eager for validation and willing to have others have a say in what he does, it makes sense that he falls into this protector role even deeper.

2)

He also wanted to be an example of excellence and make a name for himself, especially with being a second son and without a clear, solid inheritance of authority. Second sons in this feudal society are thought of as “spares” in one sense, since if their older brothers die they can take their place and inherit the family resources and the authority over the house. so he’d have felt more pressure to prove himself in the shadow of his brother (while he wasn’t much of a warrior or inclined to develop physical prowess, Viserys was also considered quite attractive before he gained weight).

3)

He supports Viserys in that he was wiling to use a group of fighters to go against Corlys and his group for Viserys’ claim before Jaehaerys I called for the Great Council of 101 A.C:

Reports had reached the court that Corlys Velaryon was massing ships and men on Driftmark to “defend the rights” of his son, Laenor, whilst Daemon Targaryen, a hot-tempered and quarrelsome young man of twenty, had gathered his own band of sworn swords in support of his brother, Viserys. A violent struggle for succession was likely no matter who the Old King named to succeed him.

(Fire and Blood; A Question of Succession)

Yet, at 16 Alysanne marries him to Rhea Royce (the Runestone heir), and while this was a good practical marriage for creating more ties to the Vale and setting up Daemon with some money through his wife’s properties, etc., Daemon did not like the atmosphere, look, anything of the Vale, probably how far away it was from King’s Landing/Viserys--thus the emotional and physical isolation. That he was basically sidelined by his family, kept apart.

He likely thought that since Viserys already had Aemma Arryn (the person who even was the scion of the Lord of the Vale, he himself didn't need to also marry another Vale woman not of his choosing). [headcanon]

Viserys did not let him annul his marriage to Rhea despite its failure. Viserys is directly involved with Mysaria losing her child with Daemon when he forced Daemon to bring back the dragon egg and send her off to Lys:

When he learned that his concubine was pregnant, Prince Daemon presented her with a dragon’s egg, but in this he again went too far and woke his brother’s wroth. King Viserys commanded him to return the egg, send his whore away, and return to his lawful wife, or else be attainted as a traitor. The prince obeyed, though with ill grace, dispatching Mysaria (eggless) back to Lys, whilst he himself flew to Runestone in the Vale and the unwelcome company of his “bronze bitch.” But Mysaria lost her child during a storm on the narrow sea. When word reached Prince Daemon he spoke no syllable of grief, but his heart hardened against the king, his brother. Thereafter he spoke of King Viserys only with disdain, and began to brood day and night on the succession.

(Fire and Blood; A Question of Succession)

4)

He was also not at all attracted to his new wife. So now he knows what it’s like to be a political tool, or he feels like more of a device than a person part of something “great”? (I say somewhat facetiously, he still is a feudal man who is very proud of his aristocratic lineage throughout all 3 of his marriages)

And so their marriage becomes barren (no kids). She comes to hates him too for not loving her home, for openly showing his disdain for it and for her, and perhaps she feels he is unwilling to do his duty like her and she feels resentment towards him and his ability to just fuck off while also being happier with him gone [headcanon].

Daemon doesn’t and never has considered her “family”, is the point nor ever to be in the same league as him, not just because she wasn't royal. Partially because Targs are and have been considered unique and nation-movers right from the Conquest in broader Westerosi culture. She is not a Targ or someone he can think of as his match or someone he thinks could do as much a a Targ can, which presents very interesting questions as to whether or not his pride can be equated to Lannister exceptionalism...I'd say that, eh. The Targs have put their money where their mouth was in most of their generations (and we the readers know that like the Starks but more apparent, the Targs are the closest to being magical beings or have the closest access to real magic) while the Lannisters are more famous and powerful in the main storyline bc of Tywin's reputation gained from the Rains of Castamere/friendship with Aerys II (a Targ) and Steffon Baratheon [the allegiance gives power trio for a while that reflected back on Tywin]. So there's a level of him not believing that they could ever relate to each other. He might have thought it was like trying to get an elephant to mate with a zebra.

I don't think that we should tell people they shouldn't dislike him for that bc yes his person can read as arrogant and he's still a prince/male who has a lot of benefits over a woman like Rhea (but not the authority she has over her own men as a female ruler in her own right, which some might argue grinds his gears more as a second son and this is actually a very interesting and valid thought...but I also doesn't think it bothered him for long to have a wife who has more practical power over others than him since his marriage to Rhaenyra saw no attempts of him barrowing over her, so that would support the idea that Rhea having this wasn't really the issue). But considering how

Still, it's not because of anything she did to him, but because she was someone who enables him to be in a position that he really does not want to be in and he believes it’s unlikely that he’d ever get any sort of glory or power all the way in the Vale, away from King’s Landing, away from the throne. It’s also probable that she also had a very different--sort of "duty is everything, sacrifice your pleasure and making compromises aside"--personality than his, thus convincing him even less to actually try to forge some sort of bond with her. Stern, but too serious, punctilious, and [for him] overly tradition-bound and scrupulous. But who knows?! [headcanon]

Laena and Rhaneyra, though? They both obviously had a lot more in common with him other than being dragonriders than he ever did with Rhea. Laena has her adventurous-ness and some daring, and Rhaenyra has pride and that “restlessness” that Viserys of HotD mentions, that unwillingness to accept a lot or assignment. They are also both his closer blood relatives, real family (remember that he grew up alone with his brother and father, a small set emotionally dependent on each other but also probably not that expressive). Those marriages were better for him, both personally and politically.

Daemon also named his kids after loved people in his life or people who will give love to his daughters.

“Baela” -- “Baelon”. “Rhaena” -- “Rhaenys”.

Viserys (II) after Daemon's own brother, Rhaenyra after her father, and both to spite/oppose Alicent & give their son the cloak of Targ-ness and kingliness: out of pride/love, the latter the stranger reason while the former the icing on the cake.

Aegon (III) after Aegon the Conqueror (king-liness and house pride) & to spite/oppose Alicent.

"Visenya", after the woman who loved her siblings and son and put them first over herself or the realm.

5)

He strategizes more logically than Aemond does and is less prone to act on his anger. Contrast this QUOTE with THIS and THIS.

6)

He specifically distrusts other houses and nonfamily bc the Targs are the pinnacle of power with their dragons, conqueror past, and prestige. He knows other lords--like Otto and pretty much all the mentioned Hightowers (think Maegor, Ceryse Hightower, and the High Septon at the time)--will always have their own agendas.

The reason why Valyrian dragonslords literally kept it in the family was to keep their control of the dragons within their respective families so people like the Lannisters (Queen Dowager Rhaena, Jaehaerys' and Alysanne's older sister) or some nondragonlord Vlayrian family couldn't then acquire dragons to use them against them.

Again, bc he and his brother and father became their own unit--and then it was just him and Viserys--that sense of needing to stick together against others would and did only strengthen.

Aemond

1)

Aemond, by contrast, has little justified reason to hate Rhaenyra like Daemon hated or grew emotionally distant from Viserys. 

While Alicent taught him to hate her, he still grew up with the assumption that he could and should destroy/rape people because his male, trueborness allows him to. His preoccupation with his maleness makes him think that he should usurp the heir, even though the law and precedent of “King’s word is law” (Viserys naming Rhaenyra as his heir and never straying) justifies his & the Greens’ treasonous actions. 

Daemon, though he hated that Viserys named Rhaenyra as heir and not him, never actively tried to depose her or his own brother. Does Daemon have his own classist entitlement and ambitions, of course! He's a very proud prince in a feudal system with a family/house with a relatively short but twisted past as monarchs. He is also the person who walked around with non-nobles like a smallfolk in KL, like those in the City's Watch and inspired people to want to follow him.

2)

While Aemond grew up dragonless for 10 years, he was surrounded by family and Hightower supporters since birth who show no sign of mistreating him, at all -- unlike in the show. He does claim Vhagar he at 10, which is impressive (while cradle-bonding is not as impressive, nor did he surpass Rhaenyra, who claimed Syrax at 7. Just saying).

He has a history where his mother teaches him and his siblings to see Rhaenyra as unfit because she has extramarital/maybe premarital sex with unassigned men and gave birth to illegitimate children. The V boys, in Alicent’s eyes, don’t deserve to live or inherit the throne because of what the Faith says about bastards and because they are in the way of her own hous, herown, and her children’s power. Bastards are socially stigmatized and unfavorable because they are believed to be inherently untrustworthy and evil (Faith of the Seven). 

By having bastards, Rhaenyra acts “unwomanly” and against the standards set for her gender–how can she be a good ruler?! 

To him, Rhaenyra is a whore and an inferior person, her sons lesser than himself because their bio parents weren’t married (rumored but we know who the daddy is, not that it matters), and duty and custom goes above everything else, as Alicent teaches him.

3)

So it is Aemond’s duty to make sure that Aegon gets the throne, and for that to happen, Rhaenyra needs to go. Preferably violently. Alicent and Otto both emphasized this to him and Aegon practically since birth, and he would have grown up with this being understood as his main and single purpose. Daemon is what he sees as the obstacle to that goal.

However, Daemon supported more out of love and regard for what he believes would maintain his family's lives and power than duty and to prove his own male privilege. But Aemond sees in Daemon a competitor and his only worthy rival because of those similarities I just listed under “Both” as well as being the person who supports the enemy of the Greens (maybe not the Visenya bit...I doubt Aemond ever seriously thought about how they share a piece of her or her beyond the idea that she was a “witch”, even though he rode her dragon and they both have a strong hand in usurping a rightful heir [Maegor vs Aegon the Uncrowned]).

And with Aemond, perhaps following duty and acting out his role, like Daemon, is a way for him to claim some sort of love from his family, but as @hamliet says, I think love is a transaction for the Hightowers and reinforced that lack in Aemond, creating a cycle of dependency and focus on gaining power through his privilege.

EDIT #1 (inspired by mononijikayu's reblog HERE):

Daemon grew up knowing Alysanne was a huge part of making policies and supporting Jaehaerys' rule; his mother, Alyssa, was a Targ woman known for her actively practicing agency, and his father Baelon never married again after her, preferring to keep the memory of her close and continue to make sure she lived on; and he grew around Rhaenys since they were both children.

Part of his deal with Rhea Royce, therefore, was that he disliked that she was totally emotionally incompatible with him (his own parents were Dragonriders and we as people/humans can and often try to find partners that match the arrangement our *healthy* parents had...if he wants to marry in the traditional Targ way [we remember that Westerosi lords are allowed and did marry first cousins], it is not discriminatory as much as it is almost typical of a nobleman to want to marry within traditions...there is no real indication that he hated Rhea's entire person just because of her looks in the book and after inspecting the context but it certainly was his excuse).

[stromuprisahat]

Princess Alyssa was brought to bed again in 84 AC. After a long and difficult labor, she gave Prince Baelon a third son, a boy they named Aegon, after the Conqueror. “They call me Baelon the Brave,” the prince told his wife at her bedside, “but you are far braver than me. I would sooner fight a dozen battles than do what you’ve just done.” Alyssa laughed at him. “You were made for battles, and I was made for this. Viserys and Daemon and Aegon, that’s three. As soon as I am well, let’s make another. I want to give you twenty sons. An army of your own!”    It was not to be. Alyssa Targaryen had a warrior’s heart in a woman’s body, and her strength failed her. She never fully recovered from Aegon’s birth, and died within the year at only four-and-twenty. Nor did Prince Aegon long survive her. He perished half a year later, still shy of his first nameday. Though shattered by his loss, Baelon took solace in the two strong sons that she had left him, Viserys and Daemon, and never ceased to honor the memory of his sweet lady with the broken nose and mismatched eyes.

Fire and Blood (George R. R. Martin)

[gotham-at-nightfall]

Valyrian Couples: Part I

Aegon I Targaryen & Rhaenys Targaryen

Aenys I Targaryen & Alyssa Velaryon

Aegon (son of Aenys) Targaryen & Rhaena Targaryen

Jaehaerys I Targaryen & Alysanne Targaryen

Baelon (son of Jaehaerys) Targaryen & Alyssa Targaryen

Viserys I Targaryen & Aemma Arryn

Rhaenyra Targaryen & Daemon Targaryen

Aegon III Targaryen and Daenaera Velaryon

Viserys II Targaryen and Larra Rogare

Daeron I Targaryen, Daena Targaryen and Baelor I Targaryen

By JotaSaraiva

PART II

[an-abyss-of-stars]

It Was Always Farewell

Lady Arienne Dayne had wed her cousin Prince Vorian Martell at a tender age, deemed as the most lovely Lady in all of Dorne and the most fitting for the role of Princess. But while the Dornish Prince had sought her out for her kindness and her beauty, his interest in her would fade soon enough as moons past by without her being able to give him what his advisors instilled he need most, an heir to his throne. And as he grew distant, Arienne became the target of old buried rumours that had plagued her since her youth. That she was not a true Dayne, not like her sisters. She had shimmering dark auburn red hair and deep wine violet eyes, many whispered that Arienne Dayne was a bastard. A secret Targaryen dragonseed born from her mother's rumoured affair with Prince Aemon Targaryen.

It was a rumour that she would come to learn was true.

It was in her blood to call to dragons, inescapable were the flames of Valyria and the call to the magnificent House Targaryen. When her eyes finally set on the bright golden lavender gaze of the visiting Westerosi Royal family. The third and youngest son of Prince Baelon...Prince Aegon Targaryen. Gods among men they truly were, what chance could she ever have had against a fate such as this.

Prologue

[dulcewrites]

'drowned in love' was amazing!!💖 now i can't help but imagine what faces those lords would pull when they come knocking on harrenhal's doors after the war and find witch queen lady of the castle alys, elysa on her arm and not one but Two white haired kids there lmao. the maesters would for sure have a field day with that event in the historical records. also aemond jr #1 and #2 (we really do need actual names for them huh💀) getting to grow up with two loving mothers is sooo important to me (very gaemon palehair - essie - sylvenna core except we can pretend alys and co. were lucky enough to not meet a similar fate and lived happily ever after since there's no mention of them in the book past that incident). i'd like to think alys and elysa would try very hard to make aemond a part of the kids' life in some way; always telling stories about him, saying how important he was to them and that he would definitely love the little ones with all his heart if he were still there etc 🥹

Thank youuuuuu.

Love the idea that harwin’s genes beat the shit out of nyra’s Targaryen one but Aemond genes win out for his kids 😭😭. Never gonna catch him slipping even while having kids. Aemond is just so… girl dad to me so I see alys having their boy and Elysa having a girl.

Now I’m super interested in how their dynamic would be described in f&b. Knowing how weirdly alys gets painted (one minute they say she bathed in blood, the next she kept Aemond from killing a messenger). I’m sure it would be the same for Elysa. They’d probably say something misogynistic about her ~stealing~ Aemond.

The maesters and lords seeing Elysa and alys

[asongoficeandfancasts]

Tags continued: Part 1 | Part 2 | Part 3 | Part 4 | Part 5 | Part 6

House Targaryen Line of Descent Since the Conquest From Aegon I to Daenerys I

[synchodai]

I get this impression that House of the Dragon doesn't get that "named" heirs aren't really the norm in Westeros. If it were that easy for someone to just give everything to their favorite child, Randall Tarly wouldn't have needed to force Sam to go to the Wall and Tywin could have simply chosen Cersei over Tyrion as heir of Casterly Rock.

If we look at the history Westeros borrows from, the concept of "naming" heirs wasn't really a thing in medieval England. Landed gentry didn't have direct say over the order of succession until the Statute of Wills in 1540. Before then, land and subsequent titles could only be inherited through agnatic primogeniture.

Agnatic primogeniture prioritized the living, eldest, trueborn son. Claims can only be passed on patrilineally. This means that a grandaughter can inherit a claim of her grandfather's titles through her father, but a grandson cannot be given the same through his mother. However, if his mother finally does have land and titles under her own name (not under her father's), only then does her son and other children enter the line of succession.

The reason it was like this was because it kept land and titles under one family. Daughters are less preferred because when they are married, they become part of their husband's family — meaning that any titles they receive will be inherited through a new line. This wouldn't be an ideal situation because it gives two families claims to the titles. The more claimants there are, the more unstable the hold the owner has.

In other words, agnatic primogeniture was practiced for stability. Because back in the day, titles weren't just property or land. They came with governorship over a people, so a stable and predictable transfer of titles was necessary to avoid civil conflicts and questions of legitimacy.

A landed lord or lady wasn't given the right to designate heirs for a few reasons:

Most of them were vassals who oversaw the land in the name of someone higher up. It technically isn't even theirs to give away (see: feudal land tenure).

The wishes of a human being are less predictable than having a determined line of succession based on birth order. What if he becomes incapable of declaring an heir either through illness or disability? What if he's captured and a bad actor forces him to name this person heir under threat of violence?

People died unexpectedly all time. This was before germ theory and modern medicine — child mortality was extremely high. With no refrigeration technology, a single poor harvest could mean dying from starvation. Bandits, cutthroats, and raiders were a constant threat. They could not afford to rely on a person choosing a different heir every time the old heir drops dead, because the landed lord/lady could die just as suddenly.

Even 21st century families stab each other in the back over who gets grandma's house — so imagine having an uncertain line of succession in the middle ages over a life-defining lordship and without a modern-day court system to mediate.

Going back to HotD, whenever Targaryens did go against the established line of succession, they could only have done it by consolidating the support of their vassals. Only royalty seemed to have the power to bend agnatic primogeniture, but even then they were beholden to it.

When Jaehaerys I ascended the throne over Aerea, it was mainly because there were those who saw Maegor the Cruel's act of disinheriting Jaehaerys as null and void. This restored Jaehaerys place in the line of succession above Aerea.

And when Rhaenys was passed over for Baelon, Jaehaerys had to convene his lords and offer compelling reasons as to why — her young age, her lack of an heir, her Velaryon last name, etc. It wasn't a given that just because she was a woman that she was ineligible. If he was doing it purely out of misogyny, he still had to legally justify his misogyny in order to strip away her rights.

Even after consolidating support, the book mentions Jaehaerys I and Viserys I's respective hold on the crown was still weakened. Even though their claims were backed by reasons cosigned by a powerful majority, they still had to ensure the security of their rule through other means. There were people who doubted their right to rule, and those people had to be placated with gifts (by Viserys) or intimidated into submission (by Jaehaerys).

So we come to Viserys I who never gave his vassals a reason why Rhaenyra should supercede his three sons other than, "I said so." Had he convened with his lords and maybe made the argument that a first marriage takes precendence over a second one, then maybe he could have set a new precedent and gathered support.

But no, he didn't. He relied on the power of his own words and the lords' personal oaths — oaths that he didn't exactly plan how he would enforce posthumously.

And the Realm did not choose to adopt a different succession law after Jaehaerys's designation of Baelon in 92 AC or the Council of Harrenhal choosing Viserys on 101 AC. If those two events did change anything, it was that now women were exempt from the line of succession for the crown and only the crown. It did not set the precedence that monarchs could freely choose heirs. It did not upend the whole system; it only made a tweak, as most lawful policy-changes do, by carving out at an exception. It was a committee, not a revolution.

Before and after the Dance, no other monarch, lord, or lady "declared" an heir that went against agnatic primogeniture, save for Dornish who have cognatic (equal-gender) primogeniture instead. Ramsay had to get rid of Roose Bolton's living trueborn son AND be legitimized by the crown in order to be recognized as heir (only a crowned monarch can legitimize baseborn children which is another world-building pillar a lot of people miss). Randall basically had to force Sam to abdicate because he wanted his younger brother to inherit instead. And of course, Tywin despite his intense hatred of Tyrion is forced to acknowledge him as his heir.

The rigidity of the line of succession is a major and constant source of conflict in the series, so it baffles me that people really thought that characters could just freely choose their heirs. That's why we have a civil war. It wasn't a misunderstanding. It's the expected consequences of someone carelessly going against a foundational tenent of the society they inhabit.