There's a similar one where Justin has twins (a boy and a girl) with Melanie and due to circumstances he has to take care of them and leave Brian, but in the end they get together again.
It's the "Songs In The Key of Love" series by Rizabeau (there is also a series of sequels "Sugar Plum Fairies").
Here's a link to Rizabeau's stories, they are ALL fantastic:
http://www.qaf-fic.com/atp/viewuser.php?uid=348