It's a Terrible Life
Fandom: Supernatural
Characters: Sam, Dean
Pairing: Sam/Dean
In which Dean only blows Sam off in the lift because he's against workplace romances, but when they start working the case they also end up fucking, and then when they get their memories back they're like whoa, that happened, and have to deal with the aftermath.
Dean Smith knows he's into guys (as well as girls, he's still Dean, except less repressed about his bisexuality), Sam Wesson hasn't considered it and is canonically bemused when Dean blows him off in the lift, but once they get to know each other and Dean makes his interest known, he finds himself not opposed.