Isaac Ketellapper was a son of Marcus Ketellapper and Rachel Bonewit. He married 4 May 1905 in Amsterdam to Leentje Frinkel, a daughter of Simon Frinkel and Jeltje Goldsmit. The couple had four children: the still at home living and unmarried Rachel, their two sons, Marcus and Simon, who lived with their families next to their parents home and Jetje who lived with her husband at Nieuwe Achtergrac…