HRH Charles's 19-Great Grandmother. PM Churchill's 18-Great Grandmother. Lady Diana's 20-Great Grandmother. HRH Albert II's 19-Great Grandmother. Louis XVII's 13-Great Grandmother. HM Juan Carlos' 17-Great Grandmother. HM Manuel II's 16-Great Grandmother. HM Umberto II's 16-Great Grandmother. `Red Baron' Richthofen's 16-Great Grandmother.