Salomon Werkendam and Jansje Roodveldt married in 1904 in Amsterdam. They were the parents of Simon, Leentje, Jesaia (who died as an infant in 1908), Isaak, a child that survived the war, Mozes and the here mentioned Gerrit and Abraham.
Stadsarchief Amsterdam, archiefkaart Salomon Werkendam
In addition, a Jokos file (number 12038) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.