Leo van Gelder was a son of Sander Leendert van Gelder and Debora Halmans. He married 6 May 1936 in Amsterdam to Heni Debora Weich from Zablotow (Poland). The couple had two sons, who both have survived the Holocaust, just like their mother.
City Archive of Amsterdam, archive card of Sander Leendert van Gelder and Leo van Gelder.