Gerardus Cats was a son of Barend Cats and the non-Jewish Johanna Martina Kool. Gerardus' father was previously married to Bertha Hachgenberg, who however passed away on 21 April 1915 and he remarried again on 31 July 1918.
From that 1st marriage, Gerardus Cats had two sisters (a twin), namely Johanna who married in 1930 and survived the war and Barendina, who was married too but who was killed in Auschwitz on 30 September together with her husband Machiel van Been. From the 2nd marriage of his father, he had two other brothers and a sister; they have survived the war, just as his parents. (his father passed in 1948)
Gerardus was unmarried and lived at home with his parents, since 21 February 1933 at the adres Hugo de Grootstraat 6b in Rotterdam. He worked in a transport company and during the war he was a member of the resistance. He was shot by the Germans on 23 February 1942 at Waalsdorpervlakte in Den Haag.
City archive of Rotterdam, family registration card of Barend Cats; municipal archive of Den Haag, certificate of death nr B644 dated 4 March 1942 and the Dutch War Grave Foundation (OGS).