sam in his early teens just starting to explore his sexuality and trying to figure out the best way to tell dean he can just bring girls to the motel— definitely not so he can watch/overhear etc. definitely not that!
Sam tries but has barely spoken a few words before he is backpedaling and mortified his hormone adled brain even tried to ask, but Dean of course thinks this is hilarious. Dean makes fun of Sam, makes all sort of peeping tom jokes etc. Sam hates him so bad but when he's jacking off later that is exactly what he's imagining.
Dean does bring a girl back to the motel, though, and obviously did not tell Sam beforehand. The only warning Sam gets is Dean's voice outside talking way too loudly and a girl's laugh. He just barely hides himself before the door opens. Dean wastes almost no time and it goes way too fast so that even if Sam did want to make his presence known and back out of whatever this is, he doesn't have the chance.
It is really hot though. Sam at first is too mortified to actually try to look, or even move in the slightest. But the girl moans and Dean lets out these low noises. Talks dirty just loud enough for Sam to hear. Sam bites his lip and begins to palm himself and forces all his remaining focus on staying quiet.
When Sam does finally look, he's a little disappointed to realize his vantage shows basically nothing of the girl, just Dean. But also, that's more than enough. Sam gets himself in hand and tries to match his pace to Dean's. It's agonizingly slow at first, so much so, even the girl complains.
Dean says something about how he wants to drag this out, but specifically he says "wanna drag this out for you, baby," and Sam knows instantly he's not talking to her. The only thing that covers Sam's moan is the girls. Dean is good enough not to look, but he gets this wicked smile that tells Sam Dean heard him.
There's a part of Sam that wants to be jealous of this girl, but he can't quite bring himself to really feel it. Dean's focus isn't even on her. This is for him, all for Sam. She just happens to be here. Sam wants to feel guilty for the thought. But Dean picks up speed and intensity suddenly and Sam tries to keep up and everything else is left by the wayside.
Sam imagines himself fucking the girl, as if he were in Dean's body, at first. Dean's hand readjusts and the shift in attention makes Sam's mind jump to Dean's hands on him, on Dean being the one to jerk Sam off in this rhythm he's not used to. Sam imagines himself under Dean, their cocks rubbing together in Dean's grasp. Sam has to bite into his other arm to keep from making a sound as he cums. But Dean's still fucking this girl, still putting on a show for him.
In a show of strength, Dean pulls the girl up and close to him, fucking up into her. Sam finally gets a good view of her, but he's already coming down from his orgasm. He watches almost detatched. He watches her expression, the lines of her exposed neck. Her tits, the parting of her legs where Dean fucks into her. Dean has a hand on her thigh and that possessive part of Sam rears its head again, and thats the first time he thinks about Dean fucking him.
Sam watches more closely, latching onto this concept. He tries to imagine what it might feel like. He's not brave enough yet to finger himself, but he does work himself up again. As he's getting close, his attention shifts back entirely to Dean. And how good Dean looks. How strong and handsome. Sam loves the vicious grin Dean gets. The confidence that normally annoys Sam after Dean comes back after getting laid. Sam almost gets it now.
There's some small sign. A shift in Dean's jaw, Dean licking his lips, something. But Sam knows that expression. Dean wants to bite. But he doesn't. The girl cums with a cry and Dean shoots a look directly at Sam's hiding spot. Just for a second. Just to let Sam know he knows exactly where he is. And that look, that hunger, that want to bite, hits Sam full force and Sam cums again.
