Four famous grandparents?

Request: I'm looking for a third generation celebrity to use in an example.

or a number of years, I've been arguing for a new (but also very old) perspective on what a racial group is: I find lacking both the "A race for everybody and everybody in his race" thinking derived from Linnaeus and the post-modern "Race does not exist" cant. Instead, I find that the most useful way to conceiving of racial groups is as a partly inbred extended family.

Somebody was recently trying to debunk this by asking, "How may racial groups are there in the world: three, six, one hundred?" My answer is: "Whatever is useful and defensible in answering the specific question you need to deal with at the moment. You should no more expect everyone to belong to a single racial groups as you would expect them to belong to a single extended family."

What I'd like to do is find a famous person, or the child of two famous people, who has four well-known grandparent, in order to make the point that everybody belongs to their mother's and father's extended families, but also their four grandparents' extended families, and so on up the family tree. For example, Arnold Schwarzenegger's kids are not only Schwarzeneggers, but also, Shrivers and Kennedys through their mother. While not bad, this is still a clunky example of how people belong to multiple extended families because nobody is familiar with the maiden name of the fourth grandparent, Arnold's mother.

So, I'm looking for a better example where all four grandparents' names are familiar. Maybe a movie star, royalty, an heiress, an athlete, or whatever. The actual third generation person might just be an obscure child of famous parents and grandparents. So, what I need two famous married people, each of whom are the children of famous people. Or spring from four famous families like, say, the Vanderbilts, Du Ponts, Tudors, or whatever, even if the individuals aren't all famous in their own right.

Steve Sailer's homepage and blog is iSteve.com