Dean smiled and after a moment or so more he stopped humming and just held onto the arm around him. He was worried too, far more than he'd let on, but just calming Sam down a little was enough. He'd just be glad to get Sam to sleep a while, even if Dean rarely got more than four hours or so. It was just better to make sure Sam slept.
He hated what had happened with Henry, and while he didn't think being a Winchester brought hope, he knew it at least brought a kind of happiness that no one else would ever quite get.