Jacob Barnstein was a son of Hartog Barnstein and Rachel Druijf. He was married in Amsterdam on 19 March 1942 to Lena Finsi daughter of Salomon Finsi and Mietje Finsi-Finsi. Their son Henri Salome was born in transit camp Westerbork on 22 February 1943.
Record of birth certificates of the Westerbork municipality, currently at the archives of Gemeente Midden-Drenthe in Beilen.
Biography