On 6 May 1755 Jacob J. first married Feytje Taelman, daughter of Douwe Harmanse Taelman (5 Aug 1689-11 May 1779) & Maria Haring (ca 1692-). Born on 7 Apr 1737.

On 15 Oct 1768 Jacob J. second married Jannetje Banta (50787) , daughter of Hendrick Jacobissen Banta (33667) (10 Jun 1716-ca 1808) & Elisabeth Benson (23 Oct 1725-8 Dec 1812). Born on 13 May 1744.