Sara Loonstijn was a daughter of Philip Loonstijn and Grietje Krijn. She married Saul Kesnig in 1938 in Amsterdam. Stadsarchief Amsterdam, archiefkaart Sara Loonstijn
In addition, a Jokos file (number 53969) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.