Siblings asking to pay amount for property and harassing

This property belongs to my Grandfather and now my Mother is the legal heir of the property as all the other siblings of her had decided.My mother was made the legal heir in 2002. As according my Mom had to pay they an amount so she told them that she will pay slowly. Now after so many years they are coming and arguing that the property rate is more so now they want more money. The property is given for rent and they are disturbing them by telling them that they will remove them anytime day or night by any means.They also have brought police n some people for scaring them.So want we should do?