What can you do when step kids are burning through stepdads money?

So, there was no POA set up beofre this? Who was taking care of his financial affairs, if he can't write checks?

It could be that their motivation was to provide him with better care, good financial oversight, and more frequent visits. Or it could be they want to get their hands on his money. You know them; I don't.

I think that Mom should see an attorney about protecting her assets from the situation you fear.

My mother is 90 and frail (though healthy). They visited him at the place we put him in and told him they should move 20 miles away, closer to them. They told him get all his bankbooks, and they (and he) went over to the old apartment to get them. The banks accounts are pretty well divided between his and hers (very little joint). They came and took his bank books. They said they would move him. He has early dementia and he agreed to go. They said they would take POA over his accounts since he can't write checks anymore. My mom is too frail to care for him. They moved him. That is where we stand.

How did they get POA? Even with POA they can't determine where he lives. Did he want to move? Did your mother protest? Are Mother and Step Father estranged?

The checking account was in StepFather's name only? Not a joint account with your mother?

Can you fill in a few more details about how this situation came to be?