How to claim share in ancestral property after mothers death ?

Sir, The disputed property was my grandfather's (my mother's father) ancestral property. My mother was his only child. Without writing any will my grandfather passed away. Later my mother also passed away in 1995 in my birth so my father got 2nd married and we moved away in 1997. Now in the mean time my grandmother on having anger on my father, she sold these properties to my grandfather's brother mentioning that her only daughter also passed away so she is selling the property in the document. she didn't mention anything about me in it. And another property of 6cents land with a house in it (which is earned by my grandfather) she donated it to her sister. 1) How much claim do i have in that ancestral property? 2)Whether she can sell my grandfather's ancestral property to any one? 3) Whether the donation of property earned by my grandfather to her sister is legal?