Sander van Gelder was a son of Joseph Leendert van Gelder and Rozetta van Gelder. He married Sara Cozijn in Amsterdam on 6 December 1939, a daughter of Abraham Cozijn and Sippora Premseler.
His siblings were Fogeltje, Salomon, Hendrina and Leendert.
City Archive of Amsterdam, archive card of Sander van Gelder and Joseph Leendert van Gelder.