HRH Charles's 17-Great Uncle. Poss. Lady Diana's 16-Great Uncle. HM Juan Carlos' 17-Great Uncle. Philippe of Belgium's 17-Great Uncle. Grand Duke Henri's 17-Great Uncle. HM Margrethe II's 16-Great Uncle. HM Beatrix's 13-Great Uncle. Wm. von Bismarck's 12-Great Uncle. `Red Baron' Richthofen's 13-Great Uncle.