Fuchs was born in Vienna, Austria, on February 13, 1930. His father, Maximilian Fuchs, was the son of an orthodox Jewish family. He turned down a career as a Rabbi, leaving his theological studies uncompleted. His father married Leopoldine. In March 1938, when the Nazis occupied Austria, Maximilian Fuchs emigrated to Shanghai. Ernst stayed together with his mother in Vienna. However, Nazi legislation made it illegal for Leopoldine to raise her son. Ernst Fuchs interned in a transit camp for children of mixed racial origin, only the formal separation from his mother prevented his deportation.