Problem realted to bakshishnama .

It is believed that you are all Hindu.

Who was 1st owner of the land in question say; Father of your big father?

How did the entire land in question came into his hands; say by inheritance?

Confirm!

 In local parlances; what is bakshisnama?

Is it say; Gift deed?

If yes, was it is properly executed /registered in O/o Registering Authority.

Apparently yes; since you have posted; kachahari.

However you may still confirm if it was before say; some notary in; kachahari premises or registered by donor in person in favor of donee by appearing in person before Registering Authority?

Was your big father sole owner of the entire land disposed by said bakshisnama?

If Yes, then during his lifetime it seems that donor (your big father) never agitated on validity and complained of any duress/fraud/undue influence.

If NO; then donor (your big father) could not gift more than his share.

In the meantime you may go thru:

Allahabad High Court

Babu Lal vs Brij Gopal And Others 

https://indiankanoon.org/doc/1733591/

dear sir

           owner of land was my grandfather[ father of big father] 

Dear sir

           owner of land was my grandfather [ father of big father].

registering authority.

It is believed that from big father you mean; elder brother of your father.

yes sir. you are right.

How did property (whole of it) owned by your grandfather came to your big father say; by valid WILL/registered Gift deed?

If your grandfather died without disposing his proeprty in his life time by a  valid registered deed say: WILL/Gift deed, then his property shall devolve equally upon all ClassI legla heirs i.e.; Mother (if alive as on date of death), Wife (if alive as on date of death), sons, daughters...........

Thus your uncle can not get yuor father's share until or unless your father has signed any valid/registered deed in favor of your uncle say; sale/gift/release/relinquishment etc dtc 

Check with your father..................if he has signed any deed?

Also check with O/o Authority and concerned officials under whose jurisdiction property falls e.g; Patwaari................and obtain mutation records with all link docs and check how much share ( and if boundaries are mentioned) your uncles owns.................and how much he has gifted.

This and innformation by your own father shall rule out any fraud/fraudulent act.

Your uncle can not gift more than his title ( by fair means) .

Son of your uncle can not sell more than his father's share ( by fair means) .

No sir my father has not signed  i know.