Jansje Koster was a daughter of Simon Koster and Bilha Sarphatie. Se was married in Amsterdam on 3 January 1933 to Joseph Plas. The couple had two children, who both survived the war. In 1941 Joseph Plas was registered at the same house, but at a different floor.
Addition of a visitor of the website and the Municipal Archive of Amsterdam, archive card of Simon Koster.