Sam and Dean were together but Dean cheated and broke Sam's heart. Sam left and had a really hard time — ended up working in a bar and was very depressed. Dean's one night stand had a baby boy and was giving him up for adoption. Dean found him and kept him. He was struggling with the baby but doing his best (baby was Mikey). Boys got back together somehow and Sam wrote a book about his awful time when they were apart. The book became a huge success and the boys were very wealthy. (Sam becomes a model later on).This is only the START of an enormous story that was written over several years. It becomes very au with Mary coming back from the dead, John having a demon-second wife, other children being born etc. It was a fantastic story but I can't remember the author. Would be very happy to find it again.