Siegmund Heinrich Cosman was born on 16 September 1864 in Kleve, Germany. He lived with his family in Düsseldorf and remained unmarried. After his siblings passed away or moved, Siegmund fled Nazi Germany in 1939 and settled in the Netherlands. Forced to leave The Hague in 1940, he moved to De Bilt. In August 1942, he was ordered to relocate to Amsterdam, where he stayed with relatives. In June 1943, he was arrested during a raid and sent to Westerbork, then deported to Sobibor on 6 July. He was murdered upon arrival on 9 July 1943, aged 78.
