can a person with an et alia deed cancel other interest in the property

A distant sibling who abused and robbed the parent and destroyed the will has suddenly filed false documents to obtain an et alia deed and since then has used it to demand money from me and things in the house. I lived with and took care of the parent and I m still residing in the home. I am bing told that he is the owner, that he can have me paying him rent and that he can ave the house apraised and sold right from under me aand he is one of 7 iblings.. I had dual power of attorney over my father and hagve been the executor off his will since the 80's.