Among their six children, one son John (1771-1839) became a major of the 3rd Dragoon Guards and ADC to his father, another Robert (1773-1838), joined the Royal Navy and rose to the rank of rear admiral.
Promoted to major-general on 28 April 1790, he commanded the 2nd (heavy) brigade of cavalry under the Duke of York and Albany in the Flanders Campaign from May 1793.
In 1794 he was with Erskine's column at Prémont on 17 April, but at the Battle of Villers-en-Cauchies on the 24th his command missed the action through a confusion in the orders that left Rudolf Ritter von Otto with just four squadrons to face 5,000 French.
Six generals—Abercrombie, Dundas, Harcourt, Garth, and Fox, who supported the pall—and the majority of senior officers of York's army attended the funeral.
Craig attributed the failure of the heavy cavalry at Villers en Cauchies "mainly to Mansel, whom after the action of the 17th [Premont] he had already reported as an incompetent officer.