HM Juan Carlos' 17-Great Grandfather. Philippe of Belgium's 17-Great Grandfather. Grand Duke Henri's 17-Great Grandfather. HM Margrethe II's 16-Great Grandfather. HM Beatrix's 16-Great Grandfather. HM Constantine II's 17-Great Grandfather. HM Harald V's 16-Great Grandfather. `Red Baron' Richthofen's 14-Great Grandfather.