property dispute

our family property is undivided.The land is on our grandmother's name.She was expired in the 90's.We resided in the city.Fifteen years ago we settled here at surajgarha Bihar.An oral partion was done without registry.For the last couple of years my uncle illegally occupied 3/4 th of our ancestral land.As we raised our voice against this injustice we were threatened and in one or two occasions beating taking the help of some of our neighbours.We were intimidated if we took the shelter of court the incident of persecuting us would be repeated again.my father had three brothers one of whom had passed away in the year 2002.Currently my father and my uncle are alive my uncle had two sons both married and a daughter married.we are four in our family my younger brother me my father and my mother.we twobrothers are unmarried.My father had also three sisters..They were all married in the 70's Please guide us what we can do to retrieve our land from the illegal possession and occupation of our uncle'sclutch