This is a position on the board. The Buffett estate gets an important board role because it represents their family’s large stake. Choosing someone in the family is consistent with this structure.

The article you’re picking the quote from is about estate taxes.

But his family inheriting his ownership of the company contradicts his statements about estate taxes in that article. And passing the chairman position to his son may even be part of a plan to pass wealth to him that avoids estate taxes.