[1] His father owned a fur shop and passed away in Berlin just before the onset of Nazi Germany while his mother died due to illness at the Bergen-Belsen concentration camp.

His sister Ilse Citroen (died with her husband at the Auschwitz concentration camp) was the mother of Sanne Ledermann, a friend of Anne Frank.

As a visual artist in photography, he used the Bauhaus Style of physical portraits, many times with the subject peering intensely into the camera.

[2] In 1919 Citroen began studying at the Bauhaus, where he started taking lessons from Paul Klee and Wassily Kandinsky (part of Der Blaue Reiter) and Johannes Itten, who became one of his biggest influences.

Citroen's work was included in the 1939 exhibition and sale Onze Kunst van Heden (Our Art of Today) at the Rijksmuseum in Amsterdam.