My experience: I've written picture book biographies of living and deceased people for educational publishers, and I've never had to get permission from anyone for them. Perhaps my publishers did that?
But I have a friend who wrote a PB biography of a deceased person for a trade publisher, and that person's estate was involved in reviewing the manuscript.
So, I think it depends.
My .02 is to write the manuscript, use reliable, first person sources, and submit it. If a publisher wants to pursue it, they can tell you next steps.