Hi again Cyndy. TGIF. It's 5 o'clock somewhere. Okay, I dug a little deeper for you. It looks like the Panther leases were in fact taken pursuant to Mineral Classified land as you suggested. There are several of them, and they are all on GLO lease forms as you would expect. Most, if not all, are in Volume 114 of the O & G Records of Culberson County, Texas. They were taken in July of 2014 and have 3 year terms. Some of the lessors are easy to match to the Declaration. For example, Alice E. Lopez @ 114/88. Robert Ortiz @ 114/96, Joe Ray Ortiz @ 114/104, Amalia M. Cox ? @114/113, possible heirs of Margete Pollock Ortiz. The heirs of Robt. L. Pollock were also easy to match: Roberta Martha Chew @ 114/45, Francis Mitchell @ 114/53, Helen Mays @ 114/62, Daniel Pollock @ 114/620, and Benita Varas @ 114/71. Lucille Sepulveda, Trustee @ 114/37 is a probable heir of Benita Sepulveda. M. Ramona Johnson is @ 114/79. There were several lessors who I really didn't know which interest that they came out of, but I am sure you probably do. Some may be the heirs of Esther. More Panther leases located were Michael Rene Gallardo @ 114/121, Victor Gallardo @ 114/130, Jorge or George Gallardo @ 114/139, Irene Guerrero @ 114/147, Virginia Skolnik @ 114/155, Antonio E. Busmante, a/k/a Tony @ 114/164, Eric Bustamante @ 114/173, Gloria Orona @ 114/80, Paul Bustamante @ 114/189.
I am not alleging that these were all of them, just the ones I was able to locate doing a cursory search. It does look like Panther took the time and effort to locate and lease the heirs, taking off from the Declaration.
I did have an opportunity to peruse the acknowledgments of the Declaration, and noticed that they were scattered to L.A. and other points west. I think Nevada was also on there. This could present a problem for anyone you hire, if in fact anyone ever calls you back. The search will not be centralized to Culberson County etc. etc. If there are any probate issues, they could easily fall under a cold case heading since it was your Grandaddy. Statute of Limitations problems could also arise regarding attacking the validity of the will. The Declaration could have been worded better and been made more clear regarding the interest of the State and Mineral Classified lands, but of course Cousin Esther did sign it, and was a party to it. The cross-conveyance language appears adequate.
I am starting to get a bad feeling about your chances of showing that Esther's heirs were not rightfully leased by Panther. You might want to table it or put it on the back burner. That is free advice, and you usually get what you pay for. If you do hire somebody, you might provide them with the above references, and clarify for them who exactly Esther's heirs are. I think I could figure out which ones are not heirs of Esther.
Other than that, I don't think I can do anything else for you. The good Wrench did a decent job of flushing out more information from you. He and others, obviously, are free to take it from here. I am going to bow out. It was a tough work week, but I don't mind doing some pro bono work here to help people like yourself out. Good luck, and I hope it all works out for you.