Iwan Jacob Jacobs was the son of Simon Jacobs and Sara Rosenberg. In 1919 he married Betje van der Horst, daughter of Salomon van der Horst and Betje Brest. The couple had four children.
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In addition, a Jokos file (number 636) 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 5658/11050).