Inheritance died when your father died!??

My family has land back in. My Great Grandmother and Great Grandfather bought more then 20 achres. My Great Grandmother and Great Grandfather had a will that stated when they pass my Grandpa and his sibilings should inherit the land and if one of the sibilings should pass away the land shall be passed to the grandchildren. Well my grandpa passed before my great grandmother. So once my great grandmother passed, my mother's uncle said to her That he had taken my grandpa off the will and that when my grandpa died so did her inheritance. My mother has the original will and are not sure if there was another will made after this one. If he does have another will, he has not provided it. My questions are as follow. If this is the only will, is it possible for this man to remove names off of the will once my great grandmother died? and What should we do?