Question: Who is Frederick Iv, Duke Of Holstein-Gottorp's maternal grandmother?
Sentence (from "Frederick IV, Duke of Holstein-Gottorp"): He was married on 12 May 1698 to Princess Hedwig Sophia of Sweden and they had an only child, Charles Frederick, who eventually fathered the future Tsar Peter III of Russia, therefore making Frederick a patrilineal ancestor to all Russian emperors after Catherine II.
Relevant evidence: No