My sister-in-law is very critical in a hosp. My brother is alive and well and competent. She gave her niece power of attorney. Niece states that she has the authority to make any decisions over my brother. That he is unable to make the right choice in finances and her care and will take over any decisions that he has to make. Being presently under stress and perplexed he is afraid that she is going to take over all matters and doesn't know what he can do to stop her. I appreciate any advise to help him resolve this situation.