Ancestral property

My mother had some land which she got from her father. Now she is no more and it is said that she had sold a major share of the property to her sisters and brothers. The whole documents(even that of the remaining land) are with them only. It was now found that they were actualy cheating my mother giving here a mere amount and getting her signed those documents without actually mentioning the amount of land. The sale was without the knowledge of me, my brother and our father. We were minors then. Can she sell the property like this. They are not willing for any settlement and the only option left is law. Her mother is still alive. The properties were also not divided uniformly over the male and females previously.That was before her mariage. Does we deserve the property? Is there any chance to get back the property. What all can we do for the same? What all they can do (even illegal) for preserving that with them?