Dad no longer wants to live with sibling because he's taking all his money. Any advice?

I would suggest a contract, which should be in place in case Medicaid is needed.

Room and board can be factored in and then a wage for caring for Mom and Dad.

Dad has to realize the cost of care if he had to pay for it. Check with agencies in the area to what they charge an hour. Check with Assist Livings to see what the monthly cost is for the two of them. This way you can show Dad what a bargain he is getting.

If your Dad is not happy there, support his move to a place that makes him happier.

It is not unreasonable for your Dad to contribute to the expenses by paying a fair share.

His excuse? I would say his reason is that he wants to be paid for his time and effort while caregiving. Paying rent is for the space and possibly the utilities. Dad should price what it would cost to have a caregiver from an agency come in and provide the services that mom needs. And then come up with an agreement to pay the son for the work he is doing. Sounds like a family meeting is in order, to figure out who is willing to do what and how much everything costs.