Grandparents

Is it ok to have the mentality of “grandparents should take care of their grandchildren because well it’s their grandchildren?!”

Backstory: I’m very fortunate to have my mom who is retired take care of my two girls, but I’m also considerate of her time and ask her permission when I need to go out or do something so I don’t just dump them on her. On the other hand my bf(their father btw) feels like it’s ok to use her as a personal babysitter.

Am I wrong for feeling someway about how he treats my mother?