Found this one sitting in a folder... apparently I forgot to post it. Hmm. Written after I saw Houses of the Holy for the first time. Enjoy! Mentions of Wincest.
Dean is lying through his teeth when he tells Sam that he doesn't believe that an angel is making civilians kill people who are planning to sin. He's lying when he says that the reason he doesn't believe this is because he doesn't believe in angels at all.
And, he's still kind of on the fence on that. Because, if there were really something watching over them, why did they keep losing their family? Why did they lose their mother? Their father? Why had Sam lost Jess? Why did the only remaining Winchesters nearly lose each other so often?
On the other hand, however, sometimes Dean thinks that maybe his baby brother -is- his angel. His Sammy. Not that he'd say that out loud. Never in a million years.
And, if Sam really is his angel, that could explain why so much has happened to their family. Which means Dean is to blame for all of it. Even what happened before.
It must have been known somewhere that he'd taint his angel. He knows it should be wrong; Sam is his brother, after all. But, they're closer than most couples are, much less any siblings they've ever seen, and he stopped caring long ago about what people think. Their lifestyle isn't exactly designed for starting new relationships. So, a few years back, before Sam left, they turned to each other. Now that they have been reunited, it's begun again.
And Dean knows that, yeah, maybe he does believe in angels. At least to some degree. Because he believes in Sam.