He's my older step brother and has moved in with her. We know he may have medical POA but we are not sure if it's been notarized. He has been added to the savings and checking accounts. Refinanced the mortgages to be added to her condo and home in Florida. My mother has Alzheimer's/ Dementia and really not all there mentally. We have been shut off from her with him screening all of her calls.
You said that your brother refinanced the mortgage, instead of took out a new mortgage. My first thought was if the mortgage rate was too steep and he refinanced at a lower rate. That would be smart. Have you talked to your brother about why he is doing things? From what you wrote, it is hard to tell if he is doing good or if he is up to no good. The main question would be if these things were done for your mother's benefit.
I wanted to determine if your mother has cognizance despite her dementia, and if so, whether she's capable of understanding the consequences of executing documents authorizing others to act in her behalf. "not all there mentally" suggests that she doesn't, and therefore the conveyances she might have made lack validity.
At this point, you're addressing legal and financial elder abuse and need to get law enforcement as well as an elder law attorney with a litigation practice involved.
Regardless, a medical POA does not grant authority to manage legal or financial affairs. You'll need to determine if your mother granted him proxy authority under a legal/financial POA, or DPOA.
If so, then I suspect there's more going on than meets the eye. Who else is available to help provide care for her? Why did this stepbrother move in? Was it pursuant to your mother's request? Are other family members near, and have they been helping out?
Given his restriction of access, you can ask local police to do a wellness check, or ask APS to do the same. That will at least give some indication whether she's being taken care of.
However, I suspect there's more of a backstory to this situation, and any answers are going to be only cursory until you provide the rest of the details, especially as to what the other siblings were doing and how this stepbrother managed to take control.
If the mortgages (more than one?) have been refinanced, stepbrother is now obligated to pay them as co-mortgagor, if that's the way the lender handled it. He would have had to provide financials that meet a lender's standards in order to be added as an obligor.
However, refinancing mortgages does not mean he's "added" to her real property assets. That requires either a Quit Claim Deed (more common in this case if they share joint ownership of the property) or a Warranty Deed (if she deeded the properties to him).
Was the stepbrother co-mortgagor on this mortgage? Was it a refinance, a HELOC, a reverse mortgage? And did it obligate her to more financial liability than she had previously? This last question is important, even though the stepbrother might be a co-mortgagor.
Perhaps I just don't have experience with "joint" mortgagors, but I'm really puzzled how someone can be added "as joint" but not co-mortgagor to avoid paying if she dies.
If that's the case, what was the purpose of being added? If he has no liability, his involvement is worthless to the mortgagee, and there was no purpose to refinancing the mortgage as your mother would probably be considered not an ideal mortgagee b/c of her age and medical condition.
Something's missing here; lenders want to be assured they'll be paid. If your mother wasn't able to understand, when she signed the new or amended mortgage the closing officer should have had a clue when the mortgage application was taken.