Land dispute

My father has two brothers(including him) and four sisters (one of them is specially abled).. After our grand mother's death, their paternal property(land) was divided between by father and my uncle with consents from all their sisters and in presence of a few elderly persons. They made a settlement in white paper which was signed by both of them and all the witnesses present there. The bathroom, latrine, kitchen has fallen under my uncle's part and they do not allow my parents to use them whereas in the settlement it was decided that my parents can use those untill they construct their own. Now, when my father had started contruction in his part, my uncle and his son are giving obstructions (even tried to beat the labourers).. They now claim that the land should be divided into three parts- two brothers' and one for the hadicapped sister. The part for handicapped sister will be owned by them as they have taken her charge(although forcefully). My uncle even filed a case making false allegations that my father is making illegal constructions without anyone's concern. My parents have shifted to a rented house from the last five months due to mental tortures. I am their only daughter, I dont know how to overcone this problem. Kindly help me out of this.. We r not financially sound and my parents are totally broken by these..