Ancestral property on father's name but his sisters trying to claim it

Tje ancestral property is on my father's name. But for building house he gave some part of that land to his 2 sister. Now his sisters are trying to sell that land. So my father asked them to return the land but they denied and filed a case against my father that he is not allowing them to build house on that land. The witnesses on the registry are my mother and grandmother. As far I know it is not legal to have family members as the witnesses. So is it possible now to win the case against them and get back the property?