Isidore Monnikendam was a son of Abraham Salomon Monnikendam and Schoontje Wijnberg. He married in Amsterdam on 22 December 1898 to Elisabeth Ziekenoppasser, daughter of Saul Ziekenoppasser and Henriette van Gelder.
The couple had six children: Abraham, Saul, Jacob, Henriette Jeanette, Margaretha …
In addition, a Jokos file (number 10580) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.