Partition records missing one sibling's name - How should I proceed when old partition records show everyone except only one?

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Hi everyone, I'm looking for advice on a land ownership issue in Madhya Pradesh

An old family partition involved 6 brothers, including my father and his eldest brother of all (my bade papa). I've searched the available records online. I can find the Khasra and Khatauni records of the other brothers from the MP Bhulekh website, showing the land allotted to them after the partition. Still, I cannot find any corresponding Khasra or Khatauni and map record for the eldest brother. I also searched the online record-room register copies covering roughly 2000 to 2011. In that register, I see entries for the other brothers showing the land they received after partition, but I cannot find my eldest brother's name or an entry showing the land allegedly allotted to him.

The problem is that my eldest brother currently claims and has been doing agriculture on a particular physical piece of land that belongs to him for years and wants to sell it to your father. But I haven't found any online record clearly connecting that land to him. I believe the land should fall under some existing Khasra number, even if his name isn't currently recorded against it.

What should I do in this situation? What should be my standard procedure?**

1) Should I go to the Tehsildar's office and search the records if the records prove his allotment?**

2) But if no records support his claim, what's the typical legal next step to establish ownership properly?

Thank you