Simon Loonstijn was a son of Joseph Loonstijn and Eva Vos. He married in Amsterdam, together with his brother Salomon on 29 October 1924 to Sara Roco.
City Archive of Amsterdam, archive card of Joseph Loonstijn .
In addition, a Jokos file (number 7628) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.