Juda Koster was the son of Hermanus Koster and Beatrix Eva de Vries. He got married to Mietje Zilverberg, daughter of Levie Zilverberg and Jetje Vos, in Emmen in 1908.
Addition of a visitor of the website
In addition, a Jokos file (number 40726) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.