Previous to the show, Booth and Rebecca were in a relationship, but then she got pregnant with Parker. Booth tried to propose to her, but she refused beacause she wasn't comfortable with making that decision.
Not much is known about their history other than Booth trying to propose to Rebecca when she got pregnant with Parker, but she turned him down.
- Episode 2: The Mother and Child in the Bay
Booth gets a call from his ex-girlfriend concerning who their son will spend the weekend with. Booth doesn't like the idea of his ex's new boyfriend moving in the same house with his son.
Brennan and Booth go to eat at the diner, where they get a visit from Booth's son, Rebecca, and her boyfriend. Booth confronts the new man and as nice as he is, Booth can't handle the idea of Parker with a new father figure, but when his ex suggests that maybe they should just leave Booth realizes that if he's going to be able to see Parker, then he's going to have to deal with things the way they are.
- Episode 5: The Truth in the Lye