Jacob Coster, a son of Barend Coster and Betje van Coevorden, was born in Rotterdam on 29 March 1912. His father runned a hat- and cap store in Rotterdam and Jacob earned his money as a merchant.
On 4 September 1940 he married Belia Meijer in Rotterdam, a daughter of Izaäc Meijer and Saartje Martiz. Belia was born in Gorinchem on 27 February 1917 and worked as a factory worker.
On 29 August 1930 t…