We are taking care of my grandmother past more than 15years, also she went to dead bed several times

We are taking care of my grandmother past more than 15years, also she went to dead bed several times aged above 80years. We taken care of her she is fine. Also she is very less locomotive, she can't even use restroom without assistance. My mother's sisters have not made a visit even during my grandmother's bad days. But they are asking pension shares ,we requested them to take care of her but they refused they not at all accepted our request. But they are asking her pension shares. They have not did anything to her, even in her those bad days. But they are asking share. Also they are saying they will file a case after her death. I need a legal solution. Hope you understand taking care of an old lady for more than 15years is not easy, what if someone asks share of her amount without doing nothing. Kindly help me