Hindu Succession Act incase of Ancestral Agricultural Property?

What is the role of the Hindu Succession Act in case of inherited agricultural property. My dad had a property division among his mum and sisters as my grandad died without leaving a will. He has 11 acres. He is now giving my brother and me an equal share (2.50 acres each) in half of his property in his will. However, he has left nothing for my mother and has decided to give the rest of the land (6 acres) to my brother when he dies. He has registered his will. Is this possible? Does my mother get anything? After all, she is his wife!! Also, the entire property was from my grandad. Nothing was self-acquired. If my mother doesn't get anything, could she file in court for an equal share?? What else can she do? I have decided to give my share to my mum. But it is very unfair to treat women different like my dad and favour sons. I just want my mum to be treated fairly after 33 years of a wasted,unhappy marriage!! Please can someone give me legal advise.