Isaac Groenstad was a son of Abraham Groenstad and Sara Engelsman. He married Jansje Isaac van Bergen in Weesp on 31 July 1890, a daughter of Isaak Victor van Bergen and Sara de Wilde.
Isaac and Jansje had six children: Betje, Abraham Isaac, Grietje, Sara, Simon and Eva.
website www.wiewaswie.nl.
In addition, a Jokos file (number 52580) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.