I've been going insane trying to find this story everywhere!  I know there are lots of posts for Dean with powers, but I've looked through them and I haven't been able to find this particular story.  I'm pretty sure it involved Dean being able to read minds/hear thoughts, and he didn't tell Sam about it for a while but Sam eventually found out - but Dean couldn't read Sam's mind.  I remember one scene where I think they were in a diner or something and Dean heard some teenager who was gay thinking about his depression/suicidal thoughts, and Dean started saying weird things about homosexuality really loudly to try to make him feel better - and then Sam (who apparently had feelings for Dean) thought that Dean was reacting to reading Sam's thoughts.
I don't remember much else besides this other than that it was Sam/Dean but not an established relationship.  Also, Dean wasn't born with the mind-reading ability - it was something he developed during/at the beginning of the story.
I really hope someone knows where to find this. Thanks!