HRH Charles's 18-Great Grandfather. Poss. Lady Diana's 17-Great Grandfather. HM Juan Carlos' 18-Great Grandfather. Philippe of Belgium's 18-Great Grandfather. Grand Duke Henri's 18-Great Grandfather. HM Margrethe II's 17-Great Grandfather. HM Beatrix's 14-Great Grandfather. Wm. von Bismarck's 13-Great Grandfather. `Red Baron' Richthofen's 14-Great Grandfather.