Rebecca Loonstijn was a daughter of Joseph Loonstijn and Eva Vos. She married in Amsterdam on 6 April1921 to Mozes Witsenhausen. City Archive of Amsterdam, archive card of Joseph Loonstijn.
In addition, a Jokos file (number 55372) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.