Like his parents, Gerhard Eylenburg was baptized a Christian but had Jewish origins. Prevented from working as a businessman by coercive regulations, he moved from Breslau to Berlin in 1936.
A former officer, he was declared unworthy of military service and had to perform forced labor for Siemens from 1940, as did his Jewish wife Eva. On January 14, 1943, Eylenburg was arrested for failing to wear the yellow star, but managed to escape by night. He sought out Colonel Wilhelm Staehle in Berlin-Frohnau. Staehle and his wife Hildegard actively supported people at risk. The colonel put Eylenburg in touch with Max Berner, who hid him in a shed in Berlin-Wittenau and from July 1943 in his summer house in Hohen Neuendorf, a village north of Berlin.
The Staehles, who were part of the resistance circle formed around Hanna Solf, were arrested in the summer of 1944, and the Eylenburgs had to find a new hiding place on July 3, 1944. They were liberated in April 1945 while living in a dilapidated shed belonging to a non-Jewish acquaintance, Reinhold Klau, in Potsdam-Babelsberg. The Eylenburgs were divorced in the summer of 1945; they did not have children.