Or, you know, the sex could be terrible between them. That was, surprisingly, at the forefront of Dean's mind, right behind the incest thing and the fact that he was realising Sam was actually able to fit several of the criteria he had for people he dated. This was just ridiculous. He wondered absently if he'd always been attracted to him, thought back to when Sam was a gangly, scrawny kid and was entirely certain he wasn't attracted to that.
"Oh, dude talks big, I wonder if he can back it up." His tone was full of amusement and... yeah, talking would actually help him get through this. Rolling his eyes at Sam's big hands pawing at his shirt, Dean swatted them away and just slid both his shirt and his t-shirt up over his head.
He was fast realising he was the bottom in this relationship and he wasn't sure if he wanted to fight that or not. Either way, he was already tugging Sam's shirt off as he ground his hips against Sam's.