Father transferring ancestral property to other people how to stop him

I am leaving with my father & step-mother. My grand father died in 29-09-2013. He had cancer, So in near june 2013, I had favored my father and tried to convinced my grand father for allowing my father for bringing step-mother to home. My grand father always knew that I and my brother is going to suffer in our life. Now, my father don't trust us. My step mother blown my father's mind. Problem is my father is transferring my grand father's property in the name of some other people including my step-mother's name. Please Advise me some good suggestion which will save my rights.