Joël Peper was a son of Abraham Peper and Esther Cohen. He married 25 June 1903 in Amsterdam Leentje Leuw, a daughter of Salomon Leuw and Keetje Goudsmit. The couple had two daughters, of whom one has survived the war. The other, Carolina, has been killed during the Shoah.
Leentje Leuw however passed away before the war in Amsterdam, on 13 May 1937.
City Archive of Amsterdam, archive card of Joël Peper and website www.wiewaswie.nl.