How to claim maintenance from father who abandoned us

My dad got separated from us 8 years ago. After separation we barely got any support from my father or his family. Infact my grandfather sold my great grandfathers property( a piece of land to be precise) and distributed the cash amongst his kids. Now that my mom asked for his support he said no to help. But he’s helping his daughter, he again is selling a property which is of 35L and giving away that cash to his daughter who’s currently not in a need of money as we do. My sisters school fees hasn’t been paid off and he’s forcing us to get together with our dad and then only he would help us. Tho am in talking terms with my father, we cannot agree on getting back together with him because of physical and mental abuse. We have registered 3 complaints against him and so did my grandfather. Please help me get the hole over this situation and claim my right. My mom is uneducated and doesn’t make enough money. And nobody is supporting us through this situation