1.Your query is highly deficient in providing details correctly and clearly. Your query 'we are trying to obtain legal possession document based on the legal heir certificate" is unclear. Do you want to get title of the shares of the property legally or 'legal possession document"? If you get legal title of the share of the property then you shall automatically get the authority to take possession of your individual shares of the said property.
2. The question "In whose name the said property stood before it was partitioned through the said unregistered partition deed?" was asked to know in whose name the title of the property was registered in the Registry office. The records maintained at the Tehshilder's office do not legally specify the ownership but the title deed registered at the registrar';s office does. You are required to inform based on which deed/document, the said title of the property stood in the name of your late father, Uncle and grandmother as claimed by you. Was the property jointly purchased by them or gifted to or willed in favour of them?
3. If the property still jointly stands in the name of your father, Uncle and grand mother as stated by you and if all of them has expired intestate, then all the legal heirs of your father and Uncle can amicably register a partition deed now as has been suggested in my earlier post.
4. The unregistered partition deed executed by your father and Uncle , since deceased, has no legal value whatsoever.
5. Even if the Tehshilder mutates your names in his records, your names do not get registered at the office of the Registrar as the title holders of the said partitioned property for which you might face problem while trying to sell your said share of the partitioned property.