Dad calls my brother to accuse us of stealing and abuse and he believes everything my dad says. We now don't speak anymore, and it has broken up family. My husband and I have been taking care of my dad for 9 years after he suffered a stroke and was paralyzed on one side. My brother even told my dad to call my job and tell them I was abusing him. My dad has survived for 9 years since his stroke, with High blood pressure, diabetes, paralysis, and now alzheimers. I have not been on a vacation in that time, and have only had one night away from home. But whenever dad gets upset about anything he calls this sibling and complains about us.
Our mother has Dementia, Narcissistic Personality Disorder, and is a Control Freak. She will lie, smear, and falsely accuse us younger siblings of doing or not doing things when she talks to my oldest sister - who is the GOLDEN child and lives 5 hours away. Golden Sister then gets on the phone and reams us out for being "mean" to our Mother - then goes on to smear us and spread the lies even further. We have been jumping through hoops trying to keep Mother satisfied, but it was NEVER enough. I had to walk away 18 months ago. No contact, which meant not spending holidays with my other family members who I dearly love. High price to pay for your sanity. Yes the guilt follows me and I feel horrible inside, but the stress caused blood pressure and other health issues and I knew I had to make a major change. Good Luck!
To be on the safe side, line up some hired home care to support him. It might be amusing to think of how much he has to learn about caring for a frail and mentally frail elder, but it wouldn't be fair on your father.
And if your brother won't do it, see if you can get a social worker or similar professional to call or email him and explain the realities of Alzheimers Disease. He has a lot to learn - but that means somebody's got to tell him.