I'm no child psychiatry expert, but it seems to me like introducing a new parent at age 11 would be pretty tough for him to really accept? I would more expect her be, like, an Aunt, someone who should be listened to and respected, but not a third parent.
The major players. Me, 30ish bi female. Gia, girlfriend of 4+ years. Clay, boyfriend/dom. Davis, ex/friend/"it's complicated." Eddie, roommate & fwb.
The supporting cast. Eric, Gia's husband. Bee, Gia and Eric's toddler. Dexter, Gia's lover. Helen, Eric's lover. Izzy and Nikki, Clay's partners. Liam, Eddie's husband.