If Sirius had a Family: Who Would be the Mother?

Err... where to start. Basically, prologue is an extended summary, first chapter is how it happens and after that it's their adventures, the kids', I mean. Also, Sirius didn't go to Azkaban and Lily and James aren't dead. They aren't friends with Peter, though. Just read it, it's too hard to try to explain. Rated T for swearing.