The green Monster - help

Boyfriend had a fwb before our relationship that got pregnant and had an abortion. They were apparently really close friends and it was just for sex.

He cut her out whenever we started going out, but got back in touch with her a couple years back - now they talk daily. He says she's just a friend, that they were really good friends before that ever happened.

Now, we have two babies together. Am I irrational for wanting her out? I keep having this dream that she's asking him "what would ours have looked like"

OMG IM HURTING JUST TYPING IT