In practice, there was not a Hitler estate - the government of Bavaria (a state in Germany) took ownership of the copyright.

Hitler did have a nephew by blood https://en.wikipedia.org/wiki/William_Stuart-Houston

and I guess a few others, but dwindling https://en.wikipedia.org/wiki/Hitler_family

https://nypost.com/2018/10/08/some-of-hitlers-last-relatives...