Owner Ship Of House Fraud Happen With Help Of Power Of Attorney

Hello I am staying in my grandfather house from last 30 years, my mother is staying from 43 years, the house is my grandfather house, but my daddy elder brother , change the name after my grandfather die, my daddy was below 18 years at that time , my elder daddy brother have 2 children , he have done fraud with us , he have made a( will ) power of attorney that full house is of his 2 children and no other person will get any piece of this house , now after serveral years , they are threatening us to go from this house , my daddy elder brother and my daddy both have expired , so now me and my mother. Are staying in house we have id and address proof, of same address, but house rent and electric city bill come my elder daddy brother name, and also power of attorney there children has so they threatening us to go from this house, and they are saying even going to court will not help and will not give any money or another house, they wants to put us on road , so what can we do legally,