Simon van der Horst was a son onf Karel van der Horst and Reintje Turksma. He married 1 August 1923 in Amsterdam to Clara van der Ven, a daughter of Simon van der Ven and Branca Polak. The couple had two children: Branca and Karel.
Simon was born in a family with seven children, of whom three children have survived the war. His other siblings, Meijer, Alida and Izaak have been killed during the Holocaust.
City Archive of Amsterdam, archive card of Karel van der Horst and website www.wiewaswie.nl.
In addition, a Jokos file (number 6930) on this household is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.The Jokos file reveals that a claim was lodged for compensation for valuables surrendered to the Lippmann-Rosenthal looting bank (L-claim, number 5452/10617).