Jonas Hakker was a son of Barend Hakker and Betje Keijl. He married Saartje Meents in Amsterdam on 24 December 1908, a daughter of Mozes David Meents and Roosje Lap. Besides the here mentioned children, they had also a son Bernardus, who was married to Esther Zwart.
City Archive of Amsterdam, archive card of Salomon Zwart and website www.wiewaswie.nl.
Biography