American High Government Officials Closely Related to Royalty

Which American high government officials have been closely related to kings, queens, emperors, or empresses?

By closely related, I mean grandparent/grandchild, grandaunt-or-granduncle/grandniece-or-grandnephew, parent/child, aunt-or-uncle/niece-or-nephew, sibling, or first cousin (all by blood, not by marriage); but I’d be open to something a bit more distant, especially if the relative is especially interesting. But I do mean just a bit more distant, so please don’t give me the many relatives of King John.

By high government officials, I mean Presidents, Vice-Presidents, cabinet officers, Senators, Representatives, federal judges, or state supreme court justices. Of course, the more select the particular job, the cooler the answer is — a cabinet officer or a U.S. Supreme Court Justice, for instance, would be cooler than a Representative or a trial court judge. This is not a trick question, so don’t say Gerald Ford (or others like him) unless you have a legitimate connection.

I have one answer in mind, but for all I know there might be more.