Do yourself and your immediate family a favor and IF you go down that path (having relatives move into the house), get everything squared away legally before your grandmother passes.
When everyone owns something, no one owns anything.
You’d be surprised how “relatives” act when their “free” gig is up. I lived through one of these “family house” situations via my Mother and it was a nightmare to get resolved. And I did get it resolved (using both legal and Don Corleone methods), although it took years off my life in the process.
Not all families are litigious.