Dean had to admit he was a little jealous of his brother as he watched him snooze late into the late morning. Not because he was asleep. No, he had come to terms with the fact that he would never be able to sleep a full nights worth. He also wasn't jealous of who is brother was sleeping with either. Definitely not! He had Cas, and that was as much Angel as he cared to handle. Sam could definitely keep his sweets loving arch angel to himself.
No, he was jealous of the way they were sleeping. Curled around each other like the apocalypse wasn't even happening. Like they didn't have a care in the world. Like they were at true peace in that moment.
Don't get him wrong, Dean loved Cas. But they never technically slept together. Cas didn't really sleep. He would sometimes lie next to Dean and watch him sleep, or when he went on one of his drinking binges he would pass out, but he never fell asleep. So Dean would never really know what is was like to have the peace that Sam had with Gabriel.
But despite his jealousy, and the fact that they had the end of the world to stop, he could not bring himself to wake the pair.