SOME women are possessive with their new babies/children. Not all.
I never was. My daughter (oldest) was co-parented by a group of us-including two other women, one of whom her father chose and I barely know. BUT-we all get along as co-parents, we prioritized the children.
Don't make assumptions based upon what you are told on this board. NO ONE HERE KNOWS YOU THREE!
Maca and GG and I knew that we would co-parent the youngest child. Maca was nervous about me having GG's baby. But GG, as the father (a man who ADORES children and this was his first bio-child) was not nervous at all about sharing the duties with Maca.
When SourPea started talking, she called Maca daddy. OTHER PEOPLE freaked the fuck out. GG did not. He was STOKED. He was thrilled that HIS baby recognized Maca as the father figure. He felt like it really consummated the family dynamic.
She's 6 now. She knows perfectly well what her biology is. She calls GG by a special pet name no one else uses. She still calls Maca daddy.
ALL of the children identify ALL three of us as PARENTS. The three older children, who also have bio-parents out of our household identify their bio parents as parents as well.
In my opinion, for our dynamic, the children actually brought all of us together. Not ONLY the three of us in a poly dynamic, but ALL of us-including the other parents.
It IS a choice how you include or disclude others in parental roles and family roles in your life.
It IS possible that they will push you out. But it is just as possible that if you take the risk, you will find that all of you are bound closer together.
"Love As Thou Wilt"