We’ve been there with both parents. My mom wouldn’t sign anything. Made it very hard to care for her. Finally hospice had the doctor declare her incompetent. Was really too late though.
Hubby’s dad didn’t tell him anything and when it came down to someone needing authority we found out his sister had taken him while he had dementia and changed everything to her name and promptly stolen all his money. It took a 3 year lawsuit to settle everything and by then dad was gone.
I don’t think parents know, or some even care, how hard they make it on their children who mostly are just trying to help them.
Your husband’s dad’s sister sounds like my wife’s uncle.
Her uncle’s father lived with us until he was 97.
She/I did all the work, he took all his money.
Hoping my sister will be a helpful ally. Dad may have early stages of dementia-he thinks we’re trying to steal his money.(and sometimes his food!-LOL.sometimes you just have to laugh)