Betje Velleman was a daughter of Zacharias Velleman and Roosje David Gans. She married Levie Hakker in Amsterdam on 11 June 1884, a son of Jonas Hakker and Sara Kok. Betje and Levie had ten children together; one child has died in infancy; three children have survived the Holocaust but her children Sara, Zacharias, Rosette, Clara, Benjamin and Anna have been killed in the Shoah. Also Betje and her husband Levie were killed in the Shoah: On 18 May 1943 both were deported from Camp Westerbork to Sobibor where they have been killed immediately upon arrival on 21 May 1943.
City Archive of Amsterdam, family registration cartd of Levie Hakker, website www.wiewaswie.nl, The file cabinet of the Jewish Council of Amsterdam, records of Levie Hakker and Betje Velleman and an addition of a visitor of the website.