David Zak was a son of Machiel Zak and Judith Olivier. He married Rachel Zomerplaag on September 4th 1895 in Amsterdam. She was a daughter of David Elias Zomerplaag and Vrouwtje Wertheijm.
The couple had no children.
David himself was born into a family with twelve children. Two of them died in childhood. The others all have been killed during the Holocaust.
City Archive of Amsterdam, family registration cards of Machiel Zak, David Zak and www.wiewaswie.nl.