Willem de Wolf was a son from the first marriage of his father Jacob de Wolf and Rebecca Blog, who passed away in 1932. Willem married Meintje Kool on 25 October 1933 in Amsterdam, a daughter of Elias Kool and Betje Lucasse. The couple had a son Jacob, who has been killed in Sobibor on 11 June 1943, together with his mother. Willem was killed there on 9 July 1943. The family resided at Plantage Kerklaan 6 III in Amsterdam.
Willem was born into a family of seven children. Two little brothers have died already, only 2 years old. The other family has been killed in the Shoah: His father Jacob, together with his wife Heintje Roeg were killed in Auschwitz; his brothers Isaak and Samuel have been killed in 1941 in Mauthausen; his brother Gerrit was killed in 1943 in Sobibor and his bother Mozes in 1943 in Auschwitz
City Archive of Amsterdam, archive cards of Jacob de Wolf, Gerrit de Wolf, Willem de Wolf, Meintje Kool, Samuel de Wolf, Mozes de Wolf, and Isaac de Wolf and an addition of a visitor of the website.