HRH Charles's 16-Great Aunt. Poss. Lady Diana's 14-Great Grandmother. HM Juan Carlos' 16-Great Aunt. HM Margrethe II's 14-Great Grandmother. HM Beatrix's 13-Great Grandmother. Wm. von Bismarck's 11-Great Grandmother. `Red Baron' Richthofen's 11-Great Grandmother.