Simon Koster was a son of Mozes Koster and Jansje Spier. He married to Bilha Sarphatie in Amsterdam on 21 November 1895 and six children were born to them: Mozes, Abraham, Marcus, Isaac, Rachel and Jansje Koster.
Municipal Archive of Amsterdam, archive card of Simon Koster.
In addition, a Jokos file (number 11706) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.