About relationship. I need help pls

Hello mga mommy. So i have here a situation. Before nung bago palang kami ng boyfriend ko we were so okay walang problema, walang cheating issue etc. Pero as days, months, pass by, things happened. Christmas year 2021, he went home to his hometown to visit sana sa parents nya. But iba yung nangyari. He invited his ex over to their house, and "it" happened. Nalaman ko because I saw pictures his sister uploaded on facebook na nandoon nga ang girl sa bahay nila. So I confronted him, umamin naman nya. To make the long story short, we got back together. Nag usap kami ng maayos at inaayos namin yung sa amin. So far we are okay na ngayon we even had a baby boy. So here the tea. We were planning na pabinyagan anak namin sa hometown nya. I agreed because time na rin yun para ma meet ko family nya. But I can sense something na balak nila i-invite yung ex na pinag cheatan ng boyfriend ko saken dati. I don't know why but that gives me so much disrespect! For a reason na may mga pinagsamahan din daw naman and minsan na rin daw naging part ng family nila yung girl. Like is that even okay? May anak na kami ang we are already building a family tapos that girl iiinvite?! They don't know how the hell I've felt before nung nangyari yung cheating incident na yun, I almost lost myself. Now our relationship is okay pero why naman ganon ang family? Pls enlighten me if tama na tong ginagawa nila.