What can be done if my relative misuses property left by ancestors?

Hello Sir/Madam, My grandfather divided his property into equal shares for my father, uncle, and aunt. If in the future, my aunt sells her share of land to my uncle, and my uncle forcefully got my grandfather to make a will, stating that whoever takes care of him will get a portion of the property, is this legal? If it is wrong, how can we file a case against them?