incompetent uncle & deceased aunt

florida

My questions is this: My aunt has just passed and her sole benefiary is my uncle who is in a nursing home diagnosed with Alheimers diease. His step daughter wanted my uncle to sign the necessary insurance papers so that she could use some of this money to bury his wife. The nursing home said this was not possible because he is not competent and does not know what he is signing. His stepdaughter does not want to tell me (his niece) or his sister how much the insurance policy is worth. In my way of thinking he is the sole beneficiary so the money is his. Also my uncle and his wife were residents of the state of New York until his stepdaughter sent hime home to myself and my mother (his sister and neice) His wife died in the New York. My mother nor myself does not have powere of attorney over his affairs but I (the neice ) have just learned that I am one of the executors over his will. I have no knowledge of what is in the will. Could you give me some advice on this. Thank you very much