Individual Details

Mary's surname as Gregory found on Bob Juch's webpage. I doubt this. A Mary Gregory married Archelaus B. Mitchell, son of Thomas Mitchell [b. 1701] and wife Elizabeth.
I found this on WorldConnect:
Name: Mary GREGORY Sex: F Birth: ABT. 1741
Father: RICHARD GREGORY b: 1695 in Westmoreland Co., VA
Mother: MILDREDGE WASHINGTON SMITH b: 1713 in of, Mecklenburg Co., VA
Marriage 1 Archelaus MITCHELL
· Married: 27 NOV 1763 in Charles City (or Charlotte) Co., VA
Since there is a definite marriage date and it's late enough that it would have to be Archelaus B., I think perhaps this is where Mary Gregory belongs. This database had nothing on the Mitchells, it was a Gregory database. It indicated that the earlier Gregorys, of an age to be contemporaries of Thomas Mitchell [d. 1736] and his wife Mary, maybe did not come to New Kent Co that early. At the time the children of Thomas & Mary, Martha, Thomas & Archelaus & perhaps Rebecca [although I find no Rebecca for this generation], were born, 1697-1705, this family of Gregorys lived in King & Queen Co, the part that became Essex Co. There weren't any spare daughters named Mary in that generation.

The Parish Registor of St. Peter's in New Kent Co VA has only these listings for Gregorys - entries for three children of William & Martha Gregory.
1755. Thomas, son of William & Martha Gregory b. Aug.22
1757 Isaac, son of William & Martha Gregory born Nov 6, baptized September
1760 Edmund son of William & Martha Gregory born Jan 25, baptized October
However, there is one entry for a John Gregory earlier:
John Gregory was killed by a fall of a horse Nov ye 5th, 1713.

Birth	Abt 1677	New Kent County, Virginia
Death	2 Apr 1727	New Kent County, Virginia
Marriage		New Kent County, Virginia - THOMAS MITCHELL

Spouse	THOMAS MITCHELL ( - 1736)
Child	Martha Mitchell (1697 - )
Child	Thomas Mitchell (1701 - )
Child	ARCHELAUS MITCHELL (1703 - )