Thank you, Steve. If I've read your message right, you have read my article as backing the idea of ballad scholars that the song originates in the Urquhart story, whereas I go to great lengths with original research, with birth and death records linked in the article, to question the validity of this idea. The section about the family's story reads:

"If we question the validity of Maidment's and Spalding's connection of the song with the Urquharts and stop trying so hard to find connections, it is by no means clear that The Young Laird of Craigstoun is based on true events. The song gives no specific names or dates; there is no evidence of a forced marriage in the family as there is in the song; no betrothal of a young woman to a boy; and therefore no one was sent away for education until he was old enough to marry. There was a marriage with a large age gap in the family [common enough], though not the same marriage as the imputed subject of the song and the gap was the reverse of that described in the ballad; and there was a father who died the year after the birth of his son. Put this way, the link of the ballad to an actual young laird of Craigstoun is either tenuous or highly confused. [*]If[*] the connection is real, the originating events have been overlaid with a thick patina of fantasy."

And later:

"Certainty is impossible but, as folk songs go, names like "Lady Mary Ann", "my lady Dundonald", and "young Craigstoun" could be as interchangeable in the development of a song as names of battlefields, seas and monarchs, and may be chosen at random from the living, the dead or the entirely fictitious, as was the Duke of Bedford."

The beautiful tune is intriguing. Martin Carthy has a talent for digging out words and tunes others have missed, and also for adding his own words or melodies without comment or giving himself any credit. I wonder if that's what he did here. Certainly, I've not come across the tune quite he way he did it anywhere else.