Answer: Sir William Gascoigne
Many of Kate’s relationships to Americans derive from the marriage of Sir William Gascoigne (d. 1487) and Lady Margaret Percy, who are ancestors of George Washington, Meriwether Lewis, Rear Admiral Richard Evelyn Byrd of the South Pole, General George Smith Patton, Jr., and Ellen DeGeneres—and of several million Americans today.
If you said King Edward III, you're also right. If you can trace your ancestry back to King Edward III—as up to 50 million Americans can—then you most undoubtedly are related to Kate (and to William)!
Are you related to Kate?
Learn more about Kate’s kin with the new book from NEHGS, The Ancestry of Catherine Middleton. Who knows? — you might be a distant relative!
Based on the work of the late William Addams Reitwiesner, a pioneer investigator into Kate's ancestry and an expert on European noble families, this book contains an “ahnentafel” (ancestor table) plus more than twenty kinship charts connecting Catherine Middleton to various figures of historical and cultural importance.