Bf and his baby mama

So my boy and his baby mama broke up when she was about 4 months. His baby is now 5 months and we just started talking. His baby mama wants him back so they can be a family but she had originally left him for her ex. I’m worried that once she finds out about me there will be a huge issue. I’m not trying to steal her baby from her or anything and we weren’t talking when they were still together. I guess I’m just scared she’s going to feel that way.

He wants nothing to do with her and doesn’t want to talk to her unless it’s when he picks up his baby from her but she’s constantly calling and trying to FaceTime him saying it’s for the baby but she never actually has him see that baby during those calls so he stopped answering them.

I feel like a bad person but he makes me so happy and I love his baby so much. I just feel like I’m wrecking a family even though they haven’t been together in so long.