Grand daughters rights on grandfathers self acquired property

Hi,there is a self acquired property of my grandfather around 600 yards and he is an central govt railway employee and after his death my father started construction in 100 yards and after that my father was passed away due to health issues and my mother also passed away within 2 years from my fathers death at the time of my father & mother death me and my sister are minors then my grandmother legally acted as a guardian under the court of law and claimed guardianship of us,and after completion my graduation i got my grandfathers railway job which was transferred to my father and after his death it was transferred to me.Now me and my younger sister are both acquired majority and my grandmother is threatening us that she will gift the property to her daughters(4 daughters well settled and all the settlements benefits are done to them by my father & grandfather)my grandmother no longer taking care of us and she even tried to kill us with poisoned food.me and my sister decided to move away from her now how to acquire our fathers and grandfathers property what was the share we will get in which way we can claim it.