John Willcox, mentioned here as the administrator of William McKnight's estate, I believe would be Thomas Willcox's son. John moved to North Carolina in 1759 which seems to fit with the timeline of this entry.
WILLIAM McKNIGHT, at present residing in Philadelphia,
Captain of a Company in the Honble, Colonel William
Gooch's Regiment of Foot, shortly to imbarque on ship-
board on an expedition against the Spaniards; dated Sep-
tember 21, 1740; appointed wife Martha, executrix, and
all property to her and his daughter Martha; witnesses;
William Moode and John Reily; administration to John
Willcox of Philadelphia, merchant, October 23, 1751, the
widow having renounced. F, p. 423.
(Source: The Pennsylvania Genealogical Magazine [Publication of the Genealogical Society of Pennsylvania], Vol. 5, 1912, pp. 174-240: Abstracts of Wills Recorded in the Administration Books, Register's Office, Philadelphia Co., Pa.; Administration Book F, 1745-1754.)