The link of the two John Burks to Richard Bourke do appear dubious and unsupported by sources & his son, John Bourke the first Earl of Mayo was born and lived in Ireland & elevated to the peerage in 1776.
John Burk's profile - Burk-353 cites extensive sources - and includes a will of Henry Burk "In the name of God Amen. The 5 day of April, 1777. I Henry Burk of Caroline County ... as my son John Burk is to pay to the said John Burk son of my son Henry Burk for the consideration " (also slaves of same names).
And also includes Burk names from Christ Church Register include:
- John Burk the Sone of Jn & Jane Burk born 16th Aug 1678 bapt 18th of May 1679.
Which suggests Burk-353 (with same DOB) might be the son of this John Burk and Jane (and possibly the grandfather or related to Henry Burk) with John B Burk - Burk-669 either a son or nephew?
It would seem more research is needed - but it does seem highly doubtful that either John Burk is the son of Richard Bourke and brother to John Bourke 1st Earl of Mayo.
And I think unlikely that Richard Bourke of Dublin (John Bourke's ) father died in Virginia (without more substantial evidence).
He may be the Richard Bourke who died Ireland in 1727 http://census.nationalarchives.ie/reels/dw/IRE_DIOC_007246604_00009.pdf
.