Sale or reconstruction right of an ancestral property

We are staying in a join family house, which is registered in a name of my Great grandmother in municipal corporation in New Delhi. She wrote an unregistered WILL stating that this property will be owned and governed by her son (My grandfather) until he is alive and after his death this property will be equally distributed among her 3 grand sons (my father and 2 bothers). After the death of my great grandmother, my grandfather wrote a registered WILL, stating the portion in which his sons are living in that house. However, he never transferred the property in his name in municipal corporation. And now he has also died. Now, one of my father's brother has used my grandfather WILL to pay house tax for his portion of property So my questions are: 1. Does a WILL written by grand father holds any validity, as it was clearly mentioned by the owner that after the death of my grand father, property will be equally distributed among her 3 grandsons 2. Do we need relinquish deed signed from sisters of my father in order to sale or reconstruct this property? 3. Without mutation, can any of the brother sale his portion in the property even if two of them have a partition deed signed based on the grandfathers WILL, however, never transferred the title in own name? 4. What is the procedure to transfer the title in own name? Thanks in advance for your advice.