Vincent,
I can SO relate to what you're going through. My 83-year old brother has dementia. He had it mildly last year. He and his wife have been coming down for Winters for 10 years. Now, they have decided to move down here full time because the little village they live in in upstate NY has no doctors, no hospital, and really nowhere to shop unless you drive 30 minutes South. His wife made the decision based on his weakness and inability to climb stairs. Their older daughter bought them the condo here and it was just steps from where I previously lived post-diagnosis. After I was dx my SIL said they would probably not be coming back (when my brother told her he no longer felt like he could drive.)
This year, everything changed. Both their daughters think living here (about 20 minutes from me) is the best thing for both of them. His wife is a very young 77 and works out three times a week. They have been married 58 years. They have not slept in the same bed for 30 years and he is a hermit. She loves to shop but has no friends. She has superficial friends she knows, both up there and down here but nobody (except me) she can confide in or depend on.
What their daughters don't know or, maybe don't acknowledge, is that I've been financially and physically supporting them for the past 10 years. Not so much this year but, when I was working, I did a lot for them. I drove them to doctors, fixed their TVs and computers, took them on outings, concerts, movies, etc. The SIL is the one who told me I would "beat" ALS.
The SIL is up North now selling their house and all the stuff she doesn't want to send to Florida. Their daughter who bought their condo for them here (they are pretty low income) is with my brother and is finally seeing just how bad he is. She had no clue because she lived five hours away and only saw them a couple of times a year. Their other daughter is in the same little town and it seems she is pushing them to move here because "there are so many more resources."