The first book which contained any information about our William Kerfoot who died in Frederick Co. VA was in 1948 the book called "Kerfoot,Kearfott and Allied Families in America" by Robert R. Kearfott. He mentioned undocumented group of another Kerfoot in early PA Richard Kerfoot. He used some information passed around by Rev. Eugene B. Jackson (buried in Prospect Hill Cemetery of Front Royal).
There was another group in Canada and I have no idea if the more modern researcher Dr. Abigail Ann Young linked to this group.
As far as I know none of these groups of Kerfoot can claim a common ancestor or foreign birth place like: England or Ireland.
D.A.R. records found on line used incorrect information that the Wm. Kerfoot who died in Frederick Co. VA wife was Margaret. This incorrect information comes from the notes of Rev. E.B. Jackson pass to my late great-uncle Hunter B. McKay and no link with the family of Col. Robert Carter (King Carter). I have not be able to establish where Wm. was born or who was his wife. FROM ACTUAL RECORDS.
Dr. Abigail Ann Young has placed entry on Find A Grave using the above incorrect information. We really do not know where Wm. Kerfoot was buried and it was his son who in American Rev. War under Gen. Washington. She has placed the name of his son George Kerfoot's wife as Margaret Peggy McCarty. This piece of information has been floated around the net and no one can say which document gives her maiden name as MCCARTY. This was someone's opinion which has been placed on line and now people think it is FACT !!
George Kerfoot who died before his father, his widow named only as Peggy and she can be found on Frederick Co. VA tax list starting 1784 down to her death 1816.
Entered-- Y marker results. Only one Y marker kit has been sold by Family Tree DNA. I have not been able to communicate with Martin Kerfoot. He has passed through to Y Search his Y marker results.His showing H1 which means "Middle East" rare outside Indian called "Romani" or "Gypsy" can be found also in Spain or Southern France. I do not think linked to our group in Frederick Co. VA. But at the moment this is all we have.
Until male Kerfoot who we know were male descends of Wm. Kerfoot of VA start doing and share their Y marker we will not really know if all these group in US are related or not.