See, here’s the thing; it’s not like he hasn’t thought about it before.
Ok, it’s not like he hasn’t thought about it a LOT.
And maybe sometimes (every time) someone mistakes them for a couple he grins just a little too wildly and plays it up a little too well. And sure, his morning shower routine lately might include this as his go to jerk-off fantasy. But that doesn’t mean anything because he’ll never act on it. You know, FANTASY and all that. So what’s getting to him, really just setting him off? Is that this is getting to him, and really just setting him off.
And really, it’s all Sam’s fault anyway. Because Dean?
Dean has everything under control.
Sure, he’s looked at Sam’s hands while he was breaking down and cleaning a sawed-off and realized they were freaking massive and, holy hell, but bet they could just about cover his dick. And maybe that one time Sam walked out of the bathroom shower-wet and barely covered by a fraying towel Dean wanted to do inappropriate things with his tongue because there were these water drops and miles of Sam’s skin and just-!
But Dean’s got everything under control. He just takes those ideas (and thoughts and images), puts them in the “fantasy” file of his mind and saves them for his showers. But this….
All right, so maybe it’s not all Sam’s fault. That stupid, ignorant, slovenly trucker started it. Ok, so, see what had happened was:
Guy was pickin’ a fight with Dean because he lost his money. Nothing new there, right? So Dean’s smiling easy, rolling his sleeves up and stepping forward to meet the challenge. But really, one overweight human? Where’s the challenge?
Anyway, so Dean’s stepping forward to meet this guy and Sam’s doing his little brother/sidekick thing and stepping up to Dean’s back. You know, protecting his weak side, making sure the fight stays fair, all that jazz. Then this idiot looks past Dean, right at Sam and says, “What, Stretch? You wanna put your pretty mouth on me too?” And that stopped them both.
Because, these things have a pattern to them, almost a script that everyone follows. The guys who do pick a fight once they figure out they’ve been hustled always pick on Dean, the hustler. They call him out and, non-fail, one of them will impugn his manly pride. Dean knows what he looks like so it’s expected, almost clockwork, for them to pop off about his girly lashes, cutesy freckles, or (and God he HATES that movie) his "purdy mouth". But Sam? Sam’s a frickin’ land giant. He steps up to Dean’s back and everyone else eyes him, making sure he’s not getting ready to join the fray. Every time, one or two would-be brawlers will melt away. That’s the natural order of things. No one picks a fight with Sam.
Except, apparently, this guy.
Right, so guy picks on Sam and it pulls them both up short. Sam just gives the guy this weird, confused look and Dean? Dean’s so surprised he actually turns to see for himself.
“Huh. He’s right.”
“Dude, now? Seriously?” Sam quirks and eyebrow at him and pointedly looks back at the trucker.
Oh, right, that guy still.
So fifteen minutes later when an ambulance has been called and the Winchester brothers are walking out of yet another bar they’ve been banned from for life, Dean takes another good look. He realizes that Sam really does have a pretty mouth. It’s wide and generous, on the verge of a smile, and his lips are all nicely pink and plump and they look kinda soft. Like, REALLY soft. In fact, Sam has an absolutely fantastic mouth, one that just begs to be fucked. Damn, how did he not notice that before? About that time Sam notices that Dean’s not moving and turns back to glare at him, expression jumping straight to Epic Bitchface #4. Oh, that’s how. Every last one of Sam’s Bitchfaces includes pursing his lips together.
“Dude, cops? Can we go, please?”
Then they leave and never look back, the end.
Well, it would have been if Dean could keep his mind out of the gutter but, whatever.
So, now Dean’s noticed and he can’t un-notice and Sam is Not. Helping. Because now that Dean’s looking? The little bitch sucks on everything. He can’t make it through a meal without sucking his fingers clean at least four times. Every time he sits down to do research he’s got a pen with him, “for notes” which he proceeds to literally suck the cap off of. Repeatedly. He wraps his lips around bottles like they’re trying to run away. And when he doesn’t have anything at hand? He sucks his lower lip in between his teeth, leaving it plumper, pinker, and shiny with spit. Yeah, this is a problem, because Sam’s oral fixation is giving Dean a fixation of his own; namely that Sam’s mouth was absolutely made to wrap around Dean’s dick.
So that’s how Dean finds himself sitting at Dickey’s (heheh, Dickey's) BBQ Pit ignoring his plate of ribs to watch Sam suck BBQ sauce off his fingers a-fucking-gain. Somehow, despite the severe warnings he keeps giving his rapidly swelling dick, his pants have been a little on the tight side for the better part of twenty minutes. Fucking Redneck, it's totally his fault.
“What’s wrong with you? You do know there’s food within striking distance?”
“Shut up, I’m just planning my attack. Go get you an ice cream cone or something if you’re so bored.”
Huffing and pulling Bitchface #7, Sam goes to the ice cream machine leaving Dean to stare at his waffle fries. Ok, so food now, jerking-off to his little brother’s distracting mouth later. Sam comes back too quickly and Dean keeps staring at his food as he shovels it down. He can do this, he can do this. Don’t look and you won’t get distracted. He can do this, he can- Oh for fucks sake! Dean’s eyes slid to Sam for a second, just one friggin’ second, and it was over.
Sam had gotten a vanilla ice cream cone and was going to town on it. Broad, flat strokes of his tongue running up the chilled treat and swirling around as he tilted and turned the cone. That- that’s just not fucking fair! Dean’s own food is completely forgotten, hand frozen halfway to his face as he watches melted cream drip down the cone and across Sam’s hand. “Damnit.”
Then Sam did the unforgivable. He put the ice cream in his mouth. Like, the Whole. Damn. Thing. Sealed his lips around it and sucked off the melty parts.
By the way, that sound? That high, desperate, needy whine? That's totally Dean.
Sam took the ice cream out of his mouth, licked his lips and said, “What?!”
And Dean would have been fine, really. But Sam was just practically deep throating an ice cream cone and then he licked his lips but he didn’t get all of it and there was this smear of white that Dean knew was ice cream but it was making Sam’s lips look come-dirty and Dean’s jeans were practically biting into him he was so hard and really, Dean just cannot be held responsible for what he did next, because a guy can only take so much before he’s just gonna snap.
He didn’t even know he was going to do it until he was licking the ice cream off Sam’s chilled lips and along his tongue.
Yeah, and that other desperate, needy sound? That’s Dean again.
So he gets that his brother isn’t kissing him back about the same time he realizes he’s kissing his brother in the first place. Heh, oops.
Jerking back, Dean starts apologizing and muttering about curses and friggin’ witches and have you noticed anything odd lately? Well, anything else? Sam just keeps blinking like he’s not really hearing any of it and says the only thing his mind comes up with. “Oh.”
“Dude, I’m sorry! I don’t know what-”
“Shut up, Dean.”
And sometimes miracles do happen, because Dean manages to stop his mouth as Sam starts looking him over.
But this right here? This is when everything changes, because Sam gets this look. This, cat-ate-the-canary, self-satisfied, tell-that-to-your-girlfriend look. He drags his lower lip up the ice cream, just as deliberately as you please, staining his lips white and watching Dean, whose eyes are zeroed in on Sam’s mouth.
Dean’s breath hitches and just like that, Sam’s up and gone, out the door, dragging Dean with him. He doesn’t even pause, just drags him round the building to a mostly blind alley, slams Dean into the brick and drops to his knees in front of him. Dean whites out before Sam’s even touched the button of his jeans.
Dean comes back to himself with Sam’s mouth over him, cold and hot and smooth and wet. And Dean just has to thrust and fuck his little brother’s mouth because, hey, that’s what it was made for. He shoots down Sam’s throat and Sam pulls back to let some of it dribble across his lips and chin before swallowing him down again.
So here’s the thing, he’s thought about this before and OK, he’s thought about it a lot. But now that he’s here and Sam’s lips are wrapped around his cock is it as good as he thought it would be? Watching Sam lick his lips Dean thinks; No, it’s better.
So Sam smiles up at Dean and rasps out, “My turn.” and give a damn that Dean’s blissed out because Dean has some pretty, cock-sucking lips and it is Sam's turn.
What, the moral of the story? That's simple: Sam's thought about this a lot and there's nothing better than a well laid plan.