My sibling is getting increasingly less mentally competent due to health issues. He was diagnosed with mental illness many years ago and takes medication but is also obese and an alcoholic. He can function as a full-time job but is making poor decisions about my mother's property and belongings since we moved her to assisted Living. We have dual POA so I cannot do anything without his okay. He wants to call the shots but the shots are not practical. Is there a way to prove him mentally incompetent? Or I do I just keep dealing with it?
You would most likely do better challenging your brother's POA based on his willingness and/or availability to serve. He is unwilling and unavailable because he is either working or drinking and hung over during his free time.
Dual POA always a bad idea. No family is completely in agreement all the time. There are so many dysfunctional families of caregivers on this site we recognize what a nightmare this would be.
Is mom competent? If so, she can change the POA anytime she wants. Does mom recognize the problem? Or is she in agreement with what bro does?
Your profile says mom is 54 with Alzheimer's/dementia. Is that correct?
Can you consult the lawyer who drafted the POA to clarify the obligation(s) you have for one another.
Is he drinking now?