Am I Wrong?

Basically My husband, son & I share a home with my mom & sister. We split the home payments. My husband pays for my portion I’m a sahm. Anyways my son is our parents first grandchild. My mother & father aren’t fond of each other. She’s mad because he never paid cs & didn’t help us financially to move into our current home. She says he’s not welcomed here ever. My sons first birthday is next year & I want to have it at our home because we have the space & saves money on renting out a place. My mother doesn’t want my father to attend & I think its wrong because he’s his first grandchild too.

She says she doesn’t care if he goes to my sons party if we rent somewhere else. My thing is that my husband pays partially for our home so who is she to tell us that my father isn’t welcomed in our home that we partially pay for. It’s different if she was paying for everything but she is not so how can she tell us who can & can’t come to the place we partially pay for. She basically want us to spend more money & rent somewhere all because she doesn’t want my father in our home. I need to know am I wrong for feeling some kind of way?

Btw we’re only living with them because she’s on disability & cannot afford her own place. Also helps with my son.