Forceful retraction under influence of outsiders - Property division

My grandfather divided the property into 2 equal parts between 2 brothers. So a few years later, when he died, two brothers mutually decided to divide the property into 3 parts, which included my mother. The reason behind this was, my father is married with 2 kids and the uncle is alone and doesn't want to get married. Now he is still single, but he wants to revoke the property back into 2 parts under the influence of some people outside and his own sister. We don't want to revoke the property and we are ready to take full responsibility of our uncle, for his old age. We want him to stay with us.