Joseph Dwinger and Kaatje Cohen had four children. On 26 April 1904 their son Simon was born. Simon Dwinger didn't survive the war, the other three children did.
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Joseph Dwinger had a photography shop on the Grachtswal in Leeuwarden. He was known throughout Friesland as a school photographer. He was married to Kaatje Dwinger-Cohen.
S. de Jong, Joods leven in de Friese hoofdstad 1920-1945. Voltooid verleden tijd (Leeuwarden, 1970) 111-112
In addition, a Jokos file (number 34307) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.