Cancellation of Release deed and gift deed.

Hello sir, we are muslim family. My Grandfather has 3 sons and 6 daughters, 1 wife. Our Grandfather's house is transferred to his eldest daughter (Zehra Sultana) by all legal heirs after his death in year 1979 through release deed (without division of property among the legal heirs.). Despite this all are living in same house. Later she made some random gift deeds on a small part of property to some siblings. Few years later many of her siblings & mother died. Now that elder sister also died (Unmarried). Now only 2 sisters and 1 brother alive out of total 10 members. These alive people have stated that as per Islamic law only those siblings who were alive at the time of the Zehra Sultana's death only they will get shares in the property. And those siblings who died before her, their children cannot claim any right over property. I have Fatwa (ruling out) from Jamia Nizamia (Islamic school) stating that transferring of property from my grandfather to his eldest daughter directly without division among legal heirs is illegal. So my question is Can we claim our share from property? Since my father died before my aunt Zehra Sultana? Can I use fatwa in court to challenge release deed? If yes, then does cancellation of Release deed results in cancellation of gift deeds as well?