Isak Isidor (also Isaac/Isaak) Oppenheimer, son of Herz Isaac Oppenheimer and Sara Heimann, married Rosa Jacob (1868–1913) and had five children: Seraphine, Hugo, Herbert, Else Margarete, and Luise. After Rosa’s death, he married Susanna Cahn (b. 1876) and had a son, Heinz (b. 1917). In 1939, Isak and Susanna fled Nazi Germany to the Netherlands. Isak died of heart failure on 20 May 1940, likely aggravated by wartime stress, and was buried in Haarlem. Three of his children—Seraphine, Hugo, and Herbert—were murdered in the Holocaust; Else, Luise, Heinz, and Susanna survived. Heinz and his mother emigrated to Israel after the war. In 2025, a gravestone was finally placed for Isak at his burial site in Haarlem.
