Whether there was any adoption taken place or not, all documents pertaining to your father, including his school certificate, death certificate and legal heirship certificate and the employer's service records contains his father's name which you say is that of your uncle and not that of your father, hence it will become difficult to establish his original father's name, especially when he is dead now. No testimony also can be obtained .

Even if you have birth certificate, it may not have his name or his father's name.

If his father's name is available in the birth certificate then you can file a suit for declaration to declare his father's name, but for that also since your father is not alive, no testimony to this effect can be given by you. 

What is the purpose that you wanted to change his father's name now?

You establish that he is your father through the substantial and relevant sources and document the same and then approach  a civil court or high court and seek declaration of legal heirs of deceased

You need to rectify the same by executing an affidavit to its effect 

For valid adoption it is necessary there should be giving and taking ceremony 

in present case there was no giving and taking ceremony nor any valid adoption deed 

birth certificate of father would reflect his biological father name 

Affidavit by his siblings would help your case 

This is a complex situation. Establishing legal heirship often involves documentation and proof of relationships. In your case, although there might not be an adoption document for your father, there are documents like the 10th certificate, ITI certificate, and employment records that incorrectly state his father's name as his uncle's. These discrepancies could complicate matters when establishing legal heirship.

Yes, affidavits from your father's living siblings—his brother and sisters—could be crucial in establishing his rightful position as a legal heir. These affidavits should ideally attest to the actual familial relationships and affirm that despite the discrepancies in documentation regarding your father's father's name, your father was indeed the biological son of your grandfather. These affidavits can serve as supporting evidence to rectify any discrepancies in official documents and reinforce the claim for your father's share of the ancestral property. They should detail the family structure, relationships, and any relevant information that supports your father's claim as an heir.

However, it's essential to have these affidavits drafted correctly, ensuring they adhere to the legal requirements of your jurisdiction. Consulting with a lawyer to prepare these affidavits and ensure their validity in court or during the legal heirship process would be highly advisable. You can reach out to us for any further assistance

- As per Supreme Court, in Hindu law, the giving and the taking of the boy ‘in adoption' was only required and nothing more and so long as it was made out that the mother of the boy gave him in adoption and the adoptive mother took him as her adopted child with the intention to adopt, no further or separate declaration of any kind was necessary.

- Hence , a ceremony for taking and giving adoption is mandatory under Hindu Law 

- If there is no evidence of conducting such ceremony , then the said adoption is not valid.

- You can approach the court for declaring that adoption invalid .