Pupboiii

Dean who hit puberty way before Sam and just jerked off when he felt like it because there is no privacy in a motel room. Sam watching out of curiosity and asking questions, Dean learning that he doesn't just not care about the audience, he likes it.

Dean teaching Sam how to make himself feel good. Demonstrating his favourite techniques on himself and Sam copying. Dean teaching Sam how to stave off his orgasm until he's begging Dean to let him come. He never even told him he needed permission, that just developed organically, and it makes Dean lose his mind.

One of them had a wet dream so they lie practically on top of each other on the dry side of the bed.

Dean being a creep and watching porn in front of Sam, sometimes not even to jerk off, but just because he's bored. Watching porn together and jerking off side by side. It progresses to jerking each other off because it's no big deal, they're basically just one person at this point. What's the big deal about helping your brother out?

Brotherly bickering over who blows who first, once they cross that line. Dean always throws scissors and lets Sam decide anyway.

Competitions for who can make the other come first, using all the tricks they learnt on each other - they know what gets each other off.

what? no hes not too close, hes just helping you with the controls, besides its getting late so its normal for you two to cuddle. dont mind the grinding, hes just getting comfy.

hey! dont get turned on, imagine how disgusted he would be to find out you were wet just from him grinding on you. his panting is normal, its hot in that room- thats why hes taking off his shirt.