#you cant have you cookie and eat it too fidds

[old-fandom]

Based off of that one Teen!Stancest + Carla threesome comic where Stanford is fucking Stanley from behind and staring daggers at Carla.

Mystery Trio scenario. Stanford has always loved Stanley, even after the whole falling out bit. They had something when they were teens but it was nothing defined, nothing concrete. They reconnect and Stanford asks Stanley to come live with him and Fiddleford in Gravity Falls. He accepts. Stanford ends up learning all of the horrible things Stanley has endured and refocuses all of his grief and shame into overprotectiveness and slight possessive behavior. Stanford wants to rekindle what they once had but has no idea how to broach the topic back to Stanley, or if he even wants that at all.

What he is certain of is that he doesn't like the way Fiddleford eyes up his brother when they're out researching. It was fine back in college when Fiddleford would eye him, fool around with him, flirt and grope him. But Stanley, his twin, his other half, his baby brother? (When did I start referring to Stanley as my baby brother?) He didn't want anyone else to have him. No one could treat him the way he needed to be treated. He was special, he was unique, he was delicate, he was Stanford's!

Stanford would never harm Fiddleford, dear god no. That is his best friend and a damn good mechanic and scientist. He loves Fiddleford very much. He just wishes he could understand that Stanley was completely and utterly off limits. He didn't mind their friendship, in fact, he encouraged it. But those lingering touches, those cheeky lines, those fluttering eyes. Those needed to come to a stop. Immediately.

Fiddleford is openly attracted to both twins and one day over drinks, asks if they ever had a threesome before. Stanley tells them they have with a girl back in high school. Stanford tightens his grip on his beer bottle while Stan regals Fiddleford of the escapades. Afterwards, Fiddleford brings up the idea that if they ever wanted to have another, he'd be willing to be the third. After much deliberation, they agree. Stanford sees this as a way to finally reclaim the relationship he had with Stanley while also warning Fiddleford not to meddle with his Stanley.

So, the day comes, and they the boys find themselves in a very similar position as they used for Carla. Stanley fucking into Fiddleford, Fiddleford on his back looking up, Stanford behind and fucking into Stanley. Fiddleford is having a great time. He feels both of them rocket into him and soon he finds himself finishing. Soon he feels Stanley following, but Ford keeps going. In his haze, he watches Stanford rail into Stanley, who in turn is still into Fiddleford. Stanford looks different, methodical, possessive, angry. He's fucking Stanley with a punishing speed, one making him cross his eyes. Fiddleford is watching between his own overstimulation and bewilderment. He can't look away, especially not with how Stanford refuses to let go of his eyesight, boring into him. Finally Stanford cums, holding Stanley close. They all pass out in bed together shortly afterwards.

Fiddleford wakes up in the night. He's naked and content. Next to him, Stanley is laying on his side, with Stanford wrapping around from behind. They're snoring in unison. He leaves them be to grab some water and something to eat in the kitchen. He cant help but think back to way Stanford fucked into Stanley, how Stanford stared at him. It was honestly a bit scary. He's down there longer than he thought he was because half way up the stairs, he hears something coming from his room. He tip toes and peeks inside, an awful, dreadful feeling dancing around his skin. Like a stranger trespassing into someone else's home.

Stanley i still on his side, whimpering softly as Stanford is whispering in his ear and leaving kisses around the side of his head. Stanford has one of Stanley's leg raises, softly pushing into him. Stanford has it placed on his own hip, while is hand is rubbing Stanley's cock. Stanley looks half asleep, moaning softly with each thrust. He's particularly noisy when Stanford sucks a hickey on his neck in a spot where Stanley can't hide it. Stanford's other hand was cradling the side of Stanley's head with his bicep, the bicep that Stanley feel asleep on. Those fingers are raking through his hair, keeping him lulled. Fiddleford watches as Stanley finally turns his head and slots his mouth with Stanford's. He feels like an awful intruder, that this is more than just some taboo sex act, more than a silly request from some horned up country boy about being shared between twins. Fiddleford leaves before he can watch them finish. He waits it out downstairs until he knows there's no more noises from the room.

Fiddleford tiptoes back into bed, now slightly warmer than he left it. Stanley has turned around, wrapped around Stanford's body, face tucked contently between Stanford's neck and the pillow. Stanford has a protective hold of him, one hand on his back and another in his hair. Fiddleford almost jumps out of his skin when Stanford addresses him.

"F."

"Y-Yeah, Stanford?"

"Don't ever make another move on Stanley again."

Fiddleford didn't need to hear the unsaid, "or else..." He nodded his head and shut his eyes.

"Goodnight, F."

"Night, Stanford."

So yeah anyway, Mystery Trio with possessive and overprotective Stanford over Stanley. Fiddleford being traumatized that his boss/best friend. It's a good time around. Especially when Stanford becomes more overtly affectionate with Stanley in the house, keeping just one eye out on Fiddleford.