Boyfriend baby mama

Story time! My boyfriend of 6 months has an 11 month baby boy (melts my heart). He ended the relationship with the baby mama the same month she conceived, roughly 5 months later her mom takes her to the doctors to find it why she’s been so sick to find out she’s pregnant. Now normally when this happens the guy would go back to the girl to try to make it work for their child however she just basically treated him poorly, always cheating and being emotionally abusive. So he wasn’t really around for her pregnancy because nobody knew if the baby was actually his or not. They’re still kids even though they’re parents and my boyfriend just turned 18, they’re still trying to make the parenthood relationship work for the baby and I love it. It just sucks and hurts my feelings sometimes because he does stuff that he doesn’t want to because he has to be nice to ensure a healthy relationship for bumpkin (the baby nick name) the baby mama is still maturing and her acts are predictable and it’s quite obvious she still has feelings for him so I do get jealous and I completely trust my boyfriend 100% it’s just that I don’t know her I only know what my boyfriend has told me about her and it irks my nerves sometimes. For Christmas he spent the night at their house and he went over for Halloween, Thanksgiving and easter for bumpkin. Don’t get me wrong, I love how he tries his hardest to be in his life, it just gets to me because the cute memories with his son is also shared with his ex girlfriend. How would you guys feel?