Here's the excerpt from Spalding (1792) and then the whole quote-- where he's called "this young boy":

The laird of Innes (whose sister was married to this John Urquhart of Leathers) and not without her consent, as was thought, gets the guiding of this young boy, and without advice of friends, shortly and quietly married him upon her own eldest daughter Elizabeth Innes.

The history of the troubles and memorable transactions in Scotland, by John Spalding, 1792

Ye heard before of the death of John Urquhart of Craigstoun, and how his eldest son John Urquhart of Leathers shortly followed; his son again departs this life upon the last of November instant. Thus in three years space the goodsire, son, and oy, died. It is said this young man's father willed him to be good to Mary Innes his spouse, and to pay all his debts, because he was young and had a good estate, whereunto his goodsire had provided him; the young boy mourning past his promise so to do, then he desires the laird of Cromartie being present to be no worse tutor to his son than his father had been to him, and to help to fee his debts paid, being then above 40,000 pounds, for the whilk several gentlemen in the country were heavily engaged as cautioners. The laird of Innes (whose sister was married to this John Urquhart of Leathers) and not without her consent, as was thought, gets the guiding of this young boy, and without advice of friends, shortly and quietly married him upon her own eldest daughter Elizabeth Innes. Now Leathers' creditors cry out for payment against the cautioners; the cautioners crave Craigstoun, and the laird of Innes his father in law (who had also the government of his estate) for their relief. The young man was well pleased to pay his father's debt, according to his promise, albeic he was neither heir nor executor to him. Yet his goodfather, seeing he could not be compelled by law to pay his father's debt, would in noways consent thereto; there followed great outcrying against him; friends met and trysted; at last it resolved in this, the creditors compelled the cautioners to pay them completely to the hazard of the sum of their estates, a'ld they got some relies, others little or none, which made the distressed gentlemen to pray many maledictions, which touched the young man's conscience, albeit he could not mend it. And so through melancholy, as was thought, he contracts a consuming sickness, whereof he died, leaving a son behind him called John, in the keeping of his mother, and left the laird of Innes and her to be his tutors, without advice of his own kindred, which is remarkable, considering the great care and worldly conquest of his goodsire to make up an estate to fall in the government of strangers. This youth deceased in the place of Innes, and was buried beside his father in his goodsire's isle in Kinedwart.

Richie