Karl Friedrich I, Duke of Schleswig-Holstein-Gottorp

Charles Frederick, Duke of Schleswig-Holstein-Gottorp was a Prince of Sweden and Duke of Schleswig-Holstein-Gottorp and an important member of European royalty. His dynasty, the Dukes of Schleswig-Holstein-Gottorp, were a cadet branch of the ancient House of Oldenburg, which at that time was ruling Denmark. His mother was a sister of Charles XII of Sweden. Charles Frederick married a daughter of Peter the Great and became the father of the future Peter III of Russia. As such, he is the progenitor of the Russian imperial house of Holstein-Gottorp-Romanov and the patrilineal ancestor of all Russian emperors starting with Peter III, except for Catherine II.