The elder of two sons of religious German-Jewish parents, Siegfried grew up in the city of Frankfurt. Upon completing his education, he became a certified public accountant in Frankfurt. In his free time he worked as a freelance music critic. While on a vacation in 1932 on the North Sea island of Norderney, he met Herta Katz, a young woman with whom he quickly fell in love.

1933-39: The Nazis had fired Siegfried from his government job because he was Jewish. Although his mother opposed the match, Siegfried proposed to Herta and she accepted. They married in June 1933. In 1934 they left for Amsterdam, where Siegfried found a job. Herta gave birth to a daughter and began a successful interior decorating business. Just before the outbreak of war in 1939, Siegfried's parents also moved to Amsterdam.