Rights of Married daughter

My maternal grand father had 20 acres of farming land. He had 4 daughters(no sons) and my mother is the youngest daughter(4th). My maternal grand father died in 1964 without writing any wil. After that My grand mom(mother's mother) took care of the familly. Meanwhile all my aunt's got married(elder sisters of my mom). My 3rd aunt(Mom's sister) and his husband convinced my grand mom and they stayed along with grand mother. They also requested my grand mother to adopt their son(actually he is grandson to my grand mother). My grand mother wrote all the assets on his name. All these assets are ancenstral properties that came my grand father, We are Hindus and My mother got married in 1978. 1. Does the adoption has any impact on property sharing. 2. My grand mother is very old now. They(My mom's 3rd sister) are taking care of her. They are claiming that they own all her property. 3. We are fighting for for right from my mother's perspective. Does my mom's sisters get any legal rights on these property. We are assuming that all the 4 sisters should get equal rights on the property since its ancestral property(it not self acquired by anyone). 4. My mom's 3rd sister already sold some property without our consent. Is it legal.