Wasn't the laws in Scotland that were most relevant, Charlie: it was the British Laws in effect at that time in the Colony of Virginia that determined his birth year.
As for who his parents were, I may never know, and I've become increasingly pessimistic about the possibility of anyone ever solving that problem. Certainly not the "name collectors" with their several-hundred-thousand-entrydatabases sans sources of any sort except a reference to a gedcom from another _presently_ living person's database that cannot possibly be verified! If one can't examine itlater, it is NOT a source. The [fill in the blank] gedcoms dated in the last decade of the 1900's are ephemera: here today, gone tomorrow. They are not and never will be a valid source citation to any certified genealogist worth his or her professional fee for that very reason!