Step mother will not tell me or my brothers where she has placed my father in AL in an effort to prevent contact with him. What can we do?

She has gotten angry and mean and is shutting us out from attempts to locate Dad and visit him. She manipulated him while he was suffering from dementia and used her POA to sell off some of his real estate (solely titled in his name) and I believe she is afraid we will upset her plans for her financial windfall. My brother is secondary POA. How do we compel her to tell us where Dad is living so that we can visit him. He is 83 and I fear does not have much time remaining. And how can my brother take over as POA since she is failing to meet her fiduciary responsibilities?