#tfw feh gives them more content than the main games

[randomnameless]

I don't think Rhea's meant to be siblings with Seteth and the others. They don't seem as close to her or Sothis, and Rhea's the only one who calls her mother. Maybe Rhea is a 1st gen Nabatean while Seteth and his brothers are 2nd or 3rd generation? Descendants of Sothis, not her direct children.

It's all HC land!

Canon-wise, they're only "relatives" and we can't even rely on the titles or form of adress Nabateans use towards each other (save Flayn and Seteth!) because they either have to pretend to not be related to the various people existing in their verse, or, in Indech'n'Macuil being called Uncle, we have to remember that "Uncle" can be a generic term for a family/familial figure in a lot of cultures, and doesn't 100% mean that this person is your parent's brother.

I type brother/sister because I'm lazy lol and it's the hc I went with fueled by the "tired relative who has to look after a younger relative" Seteth has towards Rhea in both FEH and Nopes!

But you're right, Seteth doesn't use the same words to talk about Sothis than Rhea does and might not be her direct son, but maybe a grandson or something else entirely (great grandson?).

Granted, Rhea's close attachment to Sothis and her inability - that ultimately saves the world so was it that bad at the end? - to come to terms with her death is not supposed to be seen as something positive/healthy, and in the buddhist context of Fodlan (@fantasyinvader and others wrote a lot about it if you want to check!) it's something meant as negative, as opposed to Seteth and the other Nabateans who are more detached about it.

Word of God also mentionned that Rhea's attachment and obsession with Sothis was due to her being her mother, but also, the Creator, aka a divine being/entity for Nabateans themselves!

So is Rhea so gung-ho about Sothis because she's the baby of the family, because she's Sothis' last creation or because she's the one who survived Zanado and has severe depression/self worth issues and believes only the Goddess can fix everything that she lost ?

Is Seteth less obsessed with Sothis because he is older Rhea and not "the baby", or because they didn't have the direct "creator-created/mother-son" bond and is, as you suggest, more like a grandchild and not a direct son, or is it because he doesn't have the same emotional and mental burden Rhea has so he doesn't obsess over her?

Heck, we don't even know if - vibes aside - he is older than Rhea!

Ultimately I think we're supposed to see them as close-knit and "relatives" who appreciate each other, but also share the same secret as genocide survivors trying to not be killed in this world and they care about each other a lot.

If they're not "siblings" in the correct sense (not the same mom), I think that for all intents and purpose, they're supposed to be seen and thought of as "close relatives, as close as siblings".