On 11 Jun 1724 John married Margery Card (33342) , daughter of Job Card (26 Feb 1666/7-ca 1738) & Martha Acres (15787) (26 Feb 1667/8-bef 28 May 1716), in South Kingstown, RI. Born on 19 Feb 1702 in South Kingstown, RI.

Children of John and Margery (Card) Foster:
    i. Card Foster, b. 17 Apr 1725;
    ii. Mary Foster, b. 20 Apr 1726;
    iii. John Foster b. 10 Sep 1727;
    iv. Hannah Foster, b. 18 May 1729;
    v. Christopher Foster, b. 5 Jul 1731;
    vi. Gideon Foster, b. 11 Sep 1734; and
    vii. Job Foster, b. 20 Feb 1746.