How to word this nicely to his family

Hi everyone I’ve been living with my bf for 5 years now and recently one of the little kids (his nephew) has been here every day until his brother decides to pick him up. Anyways- his mom works and does who knows what after, his dad same but they end up doing things afterwards. This little kid is starting to want me to do homework with him everyday. We have two kids of our own that are finally at the point they don’t need help, so you can imagine how thrilled I was but now they drop him off here. And his grandma/grandpa tells him to ask me to help him with homework.. am I wrong for not wanting to do it with him? I didn’t mind helping but now it’s becoming an everyday thing.

I’m also 6 months pregnant and don’t look forward to this when he doesn’t listen and I’m doing homework with him for an hour