My genetic data will be relevant even after I'm dead because my children and grandchildren share it with me. And it's a modern kind of data that didn't exist in 1925.
I hate to tell you, but even if you have never done 23 and me or anything similar, enough of your family has that your genetic data is already very readily accessible to the parties who need it.
Realistically you cant keep that secret though. There are a lot of people who share enough of your dna to reconstruct parts of it. Possibly hundreds. And all it takes is a hair folicule or spit.
You are never keeping that secret against an interested adversary.