 He was the first son of Friedrich Wilhelm Krupinski, a "Obergerichtsvollzieher" (bailiff), and his wife Auguste, née Helmke.His two younger brothers were Paul and Günther.Paul joined the "Kriegsmarine" and entered the U-boat service, and was killed in action on 11 November 1944 while serving on as an "Oberleutnant zur See" (first lieutenant), which was sunk off the Norwegian coast by the British submarine .