I've moved out of state to care for Dad who has Alzheimer's, but is still considered competent. Brother and I are co-executors for the will, but I have POAs for health and property on Dad. Bro is talking Dad into giving him "gifts"....like the only bank acct worth about $50K. The bank was not told there was a POA, so they went along with putting Bro on as joint owner. If Dad gives Bro "gifts" they don't have to be included/divided in the will. Right? Well, Dad doesn't remember doing it. He doesn't remember seeing the estate lawyer last week. He's clearly being coached by lazy Bro who hasn't worked in 3+ years. Elder Abuse lawyers aren't interested because Dad is in his own home and these cases are 1) "hard to prove," and 2) don't pay out like nursing home abuse. Dad is a Veteran, and I'm hoping to I can't seem to out-think the Evil in Bro's plans to get all the assets, have Dad declared incompetent and throw him into a nursing home, then take off in Dad's RV with the girlfriend. Anyone else deal with similar things, and what successfully worked for you?
If the ownership is tenants in common, then other rules apply. So I think the first step is to read your document then meet with the atty who wrote your POA and explain the situation.
Personally, with your financial POA, I'd clean out his account (brother be damned), open a new account in your name and Dad's, and instruct the bank that brother is not a co-signer and cannot be added as one. If they aren't cooperative on that, let them know an attorney will be contacting them. Get an elder care attorney to write a letter to the bank and have it on file.
A POA is no good if no one knows you have it. Every financial institution your dad has a relationship should have a copy, and honestly, a lot of them don't like the one you bring in and want their own paperwork done.
You have an obligation to protect your dad and his assets, so get on this immediately. Get a statement from his doctor regarding his competence to handle his affairs (you may need two), and give those copies to banks, doctors, and anyone else he does business with.
If you are POA for financial you /would normally be protecting Dad's assets, but as it is you are serving with someone you consider to be abusing Dad's finances. Not good. Who is keeping records here?
Yet, as POA for someone who is considered COMPETENT, you do not have the power to interfer. Dad is considered capable of making his own decisions. You might consider applying for guardianship, but the truth is that this is very costly, and when siblings are considered to be "at war" often the court will step in and take over guardianship.
In my own opinion, your best step forward now is to see a Lawyer and ask that he file for temporary guardianship by the state. This alone shows your good intentions to protect Dad's assets. Then give what evidence you have (as POA) that Brother is "ripping Dad off". There are a lot of "players" here: Dad, who apparently is considered competent, Girlfriend, brother and you. If Dad is competent, and considered to be so, and not designated to be otherwise, his is the only opinion that matters here. And the court will honor his wishes to lose all his money.
You may need to step away from this, as you are being ignored as a "co-POA", and cannot protect Dad. If you maintain that position with no powers you could be held culpable in future litigations involving Dad's loss of estate.
Either Dad is competent or not. If he is, then the choices are his.
If he makes choices you think imperil him, and he will not listen to you, then resign and report him to APS to open a case for possible elder abuse.
In the end, the stumbling block is that Dad is demented, but considered competent. That is a bad combo I cannot imagine beating.