Relative to your statement, "If it is his parents, Sarah may be Sarah Flaningam/Flanigan whose mother was Sarah Jennings."

My information indicates that George Flannigan (Flanningham, etc) and Sarah Jennings had the following children:
i. ISAAC3 FLANINGHAM, b. 20 Mar 1737, Gloucester County, New Jersey; d. 09 Mar 1820, Greenwich Twp., Gloucester County, New Jersey. 10.ii. PATRICK FLANAGAN, b. 04 Oct 1739, Gloucester County, New Jersey; d. 30 Jul 1817, Pennsylvania. 11.
iii. ANNE FLANINGHAM, b. 13 Nov 1741, Gloucester County, New Jersey; d. 25 Mar 1777, Gloucester County, New Jersey.
iv. SAMUEL FLANINGHAM, b. 28 Dec 1743, Gloucester County, New Jersey; d. Abt. 1804, Gloucester County, New Jersey; m. HANNAH WOOLSTON, 15 Oct 1768, Gloucester County, New Jersey4; b. Abt. 1745, Gloucester County, New Jersey; d. Aft. 1803, Gloucester County, New Jersey.
v. WILLIAM FLANINGHAM, b. Abt. 1745, Gloucester County, New Jersey; d. Dec 1774, Gloucester County, New Jersey; m. SARAH ALBERTSON, 01 Jun 1771, Philadelphia, Pennsylvania; b. Abt. 1745, Gloucester County, New Jersey.
vi. DEBORAH FLANINGHAM, b. Abt. 1747, Gloucester County, New Jersey; m. LAZARUS PINE; b. 10 Apr 1743, Gloucester County, New Jersey; d. Nov 1779, Philadelphia, Pennsylvania.
vii. PRISCILLA FLANINGHAM, b. Abt. 1749, Gloucester County, New Jersey; m. ARTHUR HAMILTON, 23 Mar 1769, Gloucester County, New Jersey; b. Abt. 1745, Gloucester County, New Jersey.
viii. ELIZABETH FLANINGHAM, b. Abt. 1751, Gloucester County, New Jersey; m. JACOB ALBERTSON, 12 Mar 1770, Gloucester County, New Jersey; b. Abt. 1750, Gloucester County, New Jersey. 12.
ix. SARAH FLANINGHAM, b. 28 Jun 1757, Gloucester County, New Jersey; d. 10 Sep 1828, Gloucester County, New Jersey.

Here's wht I have about Sarah:
SARAH3 FLANINGHAM (GEORGE2, PATRICK1) was born 28 Jun 1757 in Gloucester County, New Jersey, and died 10 Sep 1828 in Gloucester County, New Jersey. She married (1) WILLIAM J. WILKINS 27 May 1773 in Gloucester County, New Jersey11. He was born Abt. 1746 in Gloucester County, New Jersey, and died Jan 1787 in Gloucester County, New Jersey. She married (2) JAMES WOOD Abt. 1789 in Gloucester County, New Jersey, son of JAMES WOOD and REBECCA WILKINS. He was born 13 Mar 1758 in Gloucester County, New Jersey, and died 07 Jun 1807 in Gloucester County, New Jersey.

It doesn't looklike this Sarah is your Sarah.