Ginnifer Goodwin stars as Margene Heffman on HBO's Big Love.  Margene is Bill's third and youngest wife and has had three children with him: Aaron, Lester and Nell.

Bill met Marge when she worked at Henrickson Home Plus and he eventually had her serve as a babysitter for his children. 

In season two, Margene's mother came to visit and passes away in season three.

In season two, it's also revealed that Margene has a relationship with one of Bill's employees before marrying Bill.  While Bill seems to be okay with it, his eldest son, Ben, who has a thing for Margene, is very much not.  Bill ends up transferring him.

In season three, Margene decides to start her own jewelry business as she's getting sick of just being a housewife.