Bfs ex (babymomma) doesn’t want me around

So me and my bf have known each other for 6 yrs, we have a son together he is 1 yr old. He has two daughters outside the relationship one of them being 2 & the other being 3 so yeah pretty close in age. Back story me and him dated in high school for about a 1yr and broke up he was my first boyfriend and first everything. After we broke up we stayed cool no hard feelings, i than learned he was talking to a girl i had just met and i was getting cool with i immediately told her the type of guy he was at the moment all he wanted from her was sex. The girl said “oh no girl i will never let him have me” & said we should make plans to hang out , after that i didn’t hear from her for a month. I than saw a post out of nowhere her sharing a picture of her belly saying how happy she was cause she was pregnant from him & to be honest that hurt i cried but than got over it. He was never in a real relationship with her he was always talking to diff girls but was also being nice to her to remain in the baby’s life. She texted me one day to talk & we met up, she asked if me and him had been talking i told her yes as friends but nothing more i told her i knew he was messing with other girls. After that me and her became real close i was even there for the birth & so was he i know very awkward. I took care of the baby for a month after she gave birth i became attached to the baby & the baby momma started dating someone else. So her baby daddy which was my ex started talking to me & no one knew he had a gf so i did start to kinda mess with him but i distanced myself from the girl cause i didnt want to hurt her. I later found out he had a gf so i stopped talking to him . Than he came out with oh i broke up with her so me and him started going out again and a month later the girl comes out pregnant but he told me he wasnt sure if it was his cause she cheated thats why they broke up. & guess what during all that i was pregnant as well but me and him lived together after finding out i got pregnant we lived with his parents so now he had 3 baby mommas. The 1 st baby momma ended up getting pregnant from someone else so she never cared if i was around her daughter. But the middle baby momma ended up doing a dna test to show how she was his & so he has no custody , when my baby turned 3 months me and him took a break and it was only 2 weeks i later found out he had been messing with the second baby momma. So he tried to come back to me i told him only if he changed if he stopped with the lies , so we got back together moved out to our own apartment & btw the middle babymomma would never let him see the baby saying he never cared for his daughter but he would reach out and she never let him until she turned two she has been recently let him see her which is good i trust him around because he has proven he changed. The only issue is that she told him she doesn’t want me around the baby ever he told her I’m his partner that she needs to respect the relationship she said she understands and will respect it but doesn’t want me around. So whenever he goes to see her i cant go & its kinda like why you know like doesn’t she wanna get to know me (the babymomma) that way we can all have a good relationship for the kids at the end of the day its all for the kids and the baby is my sons sister. Idk what do you girls think ?