Sam is the reason Dean's awake and in his car at quarter to three in the morning. He is the reason Dean is not asleep in his lumpy, springy, but oddly warm and comfortable bed right now. He's the reason Dean drove through New York City trying to find somewhere that's open and sells Ethiopian food.
Because it's been Valentine's Day for three hours and when Dean got Sam a heart-shaped box of candy last year (like he got Sam every year growing up) Sam laughed at him and asked why he wasted twenty bucks on candy that would be gone in an hour. Dean knew it was a waste of money then but he had been trying to do something nice for the ungrateful little bastard.
Now Dean is out looking for food with names he can't pronounce, at an hour when even he should be asleep because if he tries to get it while Sam is awake he will never, ever, ever hear the end of it. Sam will laugh at him and point at him and call him a girl and then Dean will have to grow chest hair just so he can rip it out and be manly again.
But if Sam wakes up in the morning and happens to find a Styrofoam container full of... whatever the hell it is they make Ethiopian food out of, then all will be well in Dean's world. Dean will have done something nice --not sweet, nice dammit-- for his brother. Sam will have the damn food he's been whining about for the last three states and, if Dean's really lucky, Sam might be up for a little kinky "thank you” sex later on.
That's why Dean's doing it; for the sex. It has nothing to do with the way Sam smiles when Dean manages to find the only ripe grapefruit in all of Ohio. Or the sloppy kisses he gives Dean every time Dean tosses him a pudding cup. Or the way Sam laughs like a little girl when Dean spends ten dollars on yogurt on those rare trips to a supermarket. Or the way his whole face lights up when Dean buys him ice cream.
And Sam better fucking appreciate the shit Dean had to go through for this. Hell, just getting out of the fucking room was a test of his will.
Whenever they share a bed, Dean always ends up waking with Sam plastered along his back, his hand down the front of Dean's pants.
Sam isn't so much a cuddler as he is a grabby sleeper. Usually, Dean doesn't mind because, hey, how could anyone ever complain about waking up with Sam's hand cupped around their cock? But when you're trying to sneak out of bed, it makes things just a little bit difficult.
It took Dean almost an hour to wiggle himself out from underneath Sam (an hour and a half if you count the small nap Dean took after the first attempt at leaving).
And it didn't just end with the bed.
Dean drove around for what had to have been at least a few hours trying to find somewhere that sold Ethiopian food at three in the morning. When he finally found a 24-hour Ethiopian restaurant (an actual restaurant) he whooped with joy.
His sense of victory didn't last though.
Dean couldn't read half the menu and what he could read didn't help much either since he had no idea what it was.
The woman working there, Elsabet, tried to be helpful but Dean couldn't remember whether Sam mentioned tibs or wat or kitfo or any of the other things she suggested.
He must've been thinking out loud in his tired and annoyed state because the next thing he knew she was squealing and cooing at him, "Oh my God, that is so sweet! You're getting your boyfriend food! I totally thought you were getting it for like, your pregnant wife or something because we get that all the time--"
It was right about then that Dean tuned her out, both for the high-pitched, fast-paced, valley-speak she had suddenly launched into and because he really hated the word "boyfriend.” Which Elsabet apparently loved, going by how many times she had just used it in the last two and a half minutes.
Dean finally stuck a smile on his face and ordered a little more than half the menu, maxing out his current credit card. The only thing he felt bad about was that Inigo Montoya would probably no longer be able to buy him Mountain Dew and beer at the gas station off the interstate.
It'll all be worth it though for the kinky sex.
Because it's all about the kinky sex, really.
So when Dean woke up the next morning to Sam crawling on top of him and kissing him, sucking wet bruises onto his neck and murmuring things Dean wouldn't let himself hear, the only reason Dean didn't flip him over and fuck him until they were both numb was because he was tired.