KARL-FRIEDRICH I of Denmark, Duke of Schleswig-Holstein-Gottorp (1700 - 1739). He was the son of the duke Friedrich IV and the princess Hedvig Sophia of Sweden, and husband of the Grand Duchess Anna Petrovna of Russia. He was the father of the Tsar Peter III of Russia.
Princess Hedvig Sofia of Sweden (1681 - 1708) and her husband Frederik IV, Duke von Holstein-Gottorp (1671 - 1702). She was the sister of King Karl XII and Queen Ulrika Eleonora I of Sweden, cousin of the kings of Poland & Denmark.
Catalina la Grande de Rusia_1760_Ivan Argunov | Flickr - Photo Sharing!