Jacob Loonstein was a son of Emanuel Jacob Loonstein and Saartje Boutelje. He married in Amsterdam on 7 September 1892 to Naatje Speijer, daughter of Jacob Leendert Speijer and Marianna Emanuel Schrijver. Jacob and Naatje had 9 children: Emanuel, Marianne, Maurits Jacob, Herman, Isidore, Simon, Sara, Bertha and Leendert, who died in childhood as a baby.
Naatje Speijer passed away on 2 January 1919…