 Wilhelm had two sisters, Gerta Frei (1887 — presumably killed by Nazis) and Josephina Frei (1888).Wilhelm studied medicine in Freiburg, Germany, and went on to get his doctorate in Göttingen in 1913.He met Magda Frankfurter (1885–1973) when they were both studying medicine in Freiburg and was married on 12 January 1912.