Reservation of paying expenses and receiving a portion of net profits

My relative sold some of his royalties back in the 1930's. He made the reservation that he be able to pay a certain part of the expenses and in return be paid a certain amount of the net profits. The man who bought his royalties eventually deeded to his kids and/or sold them. My question is -- I am a real estate broker, and as far as I know, this reservation my uncle made would be perpetual (continual, never ending) so as one of his heirs, shouldn't I still be able to participate in mineral production on this property (ie pay my share) and receive part of the net profits?

No one would know for sure. They would want to read the reservation, determine if specific beneficiaries were named under the terms of a will, or if the interest passed under laws of descent and distribution. Ascertain for sure whether the reservation was term or perpetual, but most importantly, exactly what it said. Maybe there was a will and a mistress that you were unaware of, and he left everything to her. As people age, they don't always make the same types of sound decisions that they may have made at another time in their lives. J. Howard Marshall would be a good example.

He may have had a mistress?? ha but he was single and died unexpectedly in his 30's. His estate was probated and my grandmother and a great aunt who had no children were heirs, so I would be heir to both parties. The Sale of Royalty and Gas Royalty said it was binding on heirs, etc. I am working with an attorney but wanted feedback from this forum as I know there is a lot of good knowledge out there. Thank you very much for your reply. Any other information you might have or anyone else might have would be greatly appreciated.

More got flushed out. Something like that, I would want to read it.

What state is the royalty in question located?

It is in Oklahoma