Adjudicate the heirship in court?

We inherited forty individual land lots of minerals interest throughout Texas. After doing so investigating I found that properties in winkler, Upton and ward counties. We have a mineral deed from my dad. The problem when my great uncle sold his share, his affidavit of heirship claimed he was the last living sibling. My grandfather died 20 years after him, but told my dad about the mineral rights from my great grandmother. I was told by an agent from SM energy and EOG resources told me I have to adjudicate the heirship in court. I have an offer from patch energy for winkler section 30 block 27 of $5500 for each of us. Can you give me any advice.

You need to consult an attorney about this to review all the facts and legal documents. The affidavit wording seems odd because being the last living sibling should not give him legal title against the children of a deceased sibling if there was no probated will. Perhaps the title could be settled with the purchaser by a stipulation of interest to avoid a court dispute, assuming that the facts support your inheritance.