I can't remember where I read it, but in the fic Dean was sleeping with John for a period of time and had been keeping it from Sam. They were on the road doing hunts during the entire fic, I'm fairly sure. I think he and Sam were leading to a thing between them and they don't have sex until the end if the story. I'm pretty sure it was a chaptered story that had a happy ending where Dean decided to be with them both. I hope I'm not getting fics mixed up, I'm sure you amazing people will know what I'm talking about! Thanks in advance!