How to get share from grandmothers property

My grandmother have a share as per the will of my grandfather.My grandfather had 5 children one of them expired at a very early stage. As per the will the portions of an individual house along with the land has been divided among 4 children of my grandfather and a portion of house (top floor) has been given to my grandmother. Except the youngest son of my grandfather none of the other sons are alive. Now my uncle or the youngest son has acquired POA from my grandmother who is ill what can be done to get the grandmother's portion divided among all the grandsons so uncle can't express rights