This post of yours is most interesting in that it brings out a question -- Does Harry Newman have the correct Jacob Duvall as the wife of Miss Taylor.
Newman states that the Jacob that married Jemima Anne Taylor was born about 1748, the son of John Duvall and Anne Fowler. Admittedly, it seems that the age of 43 is a bit older than usual for a first marriage, but what we now consider usual didn't seem to be of much concern to the Duvall family, looking at their records. Besides, Lt Jacob appears to have been pre-occupied with his military career and the Revolution during his prime marying years.
Newman cites the Prince Georges County Deeds, Liber I R M, no 9, folio 27: "On November 12, 1801, 'Jemima Ann Duvall, of Prince Georges County, widow of Jacob Duvall of John' deeded to Zadock Duvall for 161 pounds her dower rights [sic] or 34 acres in 'Mary's Delight' which her husband had conveyed to the said Zadock Duvall."
This sure seems to be documented proof that Jemina was married to the son of John. This would indeed be the Jacob born about 1748 though and not the Jacob born 1771.
Can you offer any proof that the Jacob b 1771 was Jemima Taylor's wife? Now I certainly admit that based solely on the marriage date, 1991, this Jacob would seem a likely choice, but the evidence would seem to be to the contrary.
Leaning heavily on Newman's work, I conclude that the Jacob who married Jemina Anne Taylor has the following ancestry:
+-5. Massiot Duvall (b.1604) +-4. Mareen Duvall the Emigrant (b.1630 d.1694) |+-5. Margaret Orbin (b.1608) +-3. Mareen Duvall the Younger (b.1680 d.1741) |+-4. Susannah Brashear (b.1650 d.1692) +-2. John Duvall (b.1712 d.1791) ||+-4. John Jacob Jr. (b.1631 d.1726) |+-3. Elizabeth Jacob (b.1683 d.1752) ||+-5. Richard Cheney Sr. |+-4. Anne Cheney (b.1660 d.1730) |+-5. Charity Woods / Ryan 1. LT JACOB DUVALL (b.1748 d.1800) |+-3. Thomas Fowler +-2. Anne Fowler (b.1713) |+-4. William Ijams (b.1640 d.1703) +-3. Susannah Ijams (b.1679) |+-5. Richard Cheney Sr. +-4. Elizabeth Cheney (b.1648 d.1725) +-5. Charity Woods / Ryan
Any additions or corrections, along with the proof to contradict Harry Newman, are certaily appreciated.As additional records come to light, it is certainly possible to find errors in Newman's works, and I am certain that no one would appreciate any corrections more than he would have.