[1] In the summer of 1761, at the house of Lord Alva in Mylnes Square in Edinburgh, he married sixteen year old Mary Maxwell of Reston (b.1745) in Kirkcudbright, the daughter of the late William Maxwell (1711-1760) and his wife Elizabeth Hairstares (who had remarried Charles Erskine, Lord Tinwald a.k.a.
Her sister Wilhelmina married John Campbell, Lord Glenorchy.
[2] The couple attended the coronation of George III in London on 22 September 1761, and all remarked on the beauty of his wife.
[2] The couple were buried together in a single ceremony in the family plot in Holyrood Abbey in Edinburgh on 9 August 1766.
[2] A pair of flintlock pistols gifted by William in his role as commander of the 56th Foot to Captain James Sutherland in 1763 sold for £44,000 in 2021.