Franco mentions to Sean that his mother has been dead for 10 years. The audience knows this to be false because in season 1 we first meet Franco's mother who watches out for his daughter before having to give her back to Franco when his dad has a stroke.
While talking about Mothers in the locker room, Franco states his Mother died 10 years ago, even though she was alive and on screen in season one, and has been mentioned as being alive several times since then.