Most Helpful Guy
? ? You two are breaking up because he has hostility to your mother coming to see her (your mother's) grand daughter?
Okay, I do not understand, nor do I care, why he is so hostile to her visiting. Unless she is interfering in how your household functions.
By chance, does your mother make suggestions? And do you pay attention to her advice? Is your boyfriend really pissed that he was with you, but now he is with "you-and-your-mother" instead of you alone?