Boyfriend's grandma's dog

We have watched her dog before. He's sweet. But he's not a fan of our dog. She was in a nursing home but wanted out, so they got her an apartment with in home care. Well she hasn't been doing her physical therapy, she's been falling, and can't take care of herself. She's being readmitted to the nursing home. And we're stuck with the dog. I just feel like it's going to be more of a hassle than we need. I don't want to turn him away because he doesn't have anywhere else to go and it's my boyfriend's childhood dog. Anyone have any advice on this situation? I just really hope my boyfriend helps with the dogs and house, I'm home more than he is so I feel like he's going to put it all on me.