Raphael Hekster and Judith Veerman married in 1902 in Amsterdam. They had six children, among whom Simon, Abraham and the here mentioned Nico.
Stadsarchief Amsterdam, archiefkaart Raphael Hekster
In addition, a Jokos file (number 346) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.