This is probably a wild shot seeing as I can only remember a few bits but you guys are pretty awesome so hopefully you can help me out :) 
Its a Dean/Sam fic that is set pre-series and the only thing that I know for certain that happens it is Sam is lusting over Dean but Dean doesn't let anything happen. Sam applied for Sanford and left the application or a letter out knowing that Dean would see it and would stop him from leaving by entering into a sexual relationship with him.  Oh and I think Sam entered a relationship with an OFC that was pretty kinky and she sorta knew that Sam either lusted over his brother or was gay and she encouraged him.
I know it was a pretty long fic and I seem to remember that it was pretty well known throughout fandom but that is sorta all I know.
Hope someone can help me :)

Edit: Found!