Marcus Blindeman and Ettje Frank married in 1909 in Amsterdam. They had three children: Machiel, a child that survived the war and the here mentioned Helena.
Stadsarchief Amsterdam, archiefkaart Marcus Blindeman
In addition, a Jokos file (number 12316) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.