You have to consider all your options but once you give up the rights, you've lost them forever. Personally, I'm a fan of holding on to any mineral rights I can get my hands on.
Confer with an attorney who specializes in this practice of mineral rights
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But that's me. I don't know your financial situation or the lease activity around Alvin.
But every situation is different.
You might ask the attorney handling the estate of your realtive what they think.
They're probably local and might have a better idea of values and legalities.