1. In whose name the property is in the BBMP records at present?.
2. Whether your grand father had executed a "WILL" or did he die intestate(without executing a 'WILL').
3. Whether your grand mother is alive?.
4. If your grand father had executed a "WILL", the property would devolve to the beneficiaries as per the contents of the "WILL".
5. Assuming that your grand father died intestate and the property is still in your grand father's name in the official records, then the property would devolve in equal proportion to your grand mother(if alive) & his children, i.e., 1/8th share each. If your grand mother is not alive, then 1/7th share to each child of your grand father.
6.As stated by you, your father and his 3 sisters are dead and each of their shares would devolve to their respective family members viz., spouse & children of deceased legal heirs.
7.You can get Encumbrance Certificate from the jurisdictional Sub-Registrar's Office.
8. If the Khatha is not available for the property, then the same can be obtained from BBMP office by paying the statutory fee.
9. Signature of each and every legal heir is essential, i.e., all the children of your grand father. In case of deceased legal heir/s, signature of their family members is essential.