I have power of attorney for my parents. and my Dad has Alzheimer's.I have POA for my parents. and my Dad has Alzheimers. My brother moved in temporarily while he sells his house and looks for a new one. This caused my Dad to have nightly hallucinations which we now have under control with meds. No my brother wants to move his girlfriend in and I'm afraid it will have a negative affect on my Dad and make us increase his meds. My Dad has stated he doesn't want my brother to live there anymore and he doesn't want the girlfriend moving in. Since I have POA can I block him from moving his girlfriend in?
As for your parents, maybe it is time for them to downsize [I know, easier said then done], it would make it much easier on your Mom as she will have her hands full taking care of your Dad as his Alzheimer's progresses. She wouldn't be able to take of him plus take care of a house.
If one of my relatives approached my folks with a story about needing a place to stay they would probably feel pressured to allow it. If I were to get wind of it before hand I would confront the relative in no uncertain terms and try to keep them out in any way I can. I put a stop to a relative dumping his kids off on my parents who are mid eighties. He's a good person but I told him I would not allow this.