This family was from Montréal, Prince Edward Island and Boston.

Dr. Agret A. Mackay, after completing his secondary school education at Montreal High School, entered the Faculty of Medicine of McGill University from which he graduated in 1913. Following two years' internship at the Royal Victoria Hospital, he went overseas with the 42nd Battalion, Black Watch (R.H.R.) of Canada as senior medical officer. On his return to Montreal, Dr. Mackay entered private practice as a neuropsychiatrist and became medical director of the M.A.A.A. He was consultant in neurology at the Montreal General and Verdun Protestant Hospitals, as well as being medical director of the Montreal Forum in which capacity he was club physician to the Montreal Maroons, and later the Canadiens. (Canadian Medical Association Journal v. 63, pg. 415, 1950)

Rev. Alexander Bissett Mackay was born on March 22, 1842, in Montrose, Angus, Scotland.

He was a Presbyterian clergyman. He served at the Crescent Street Presbyterian Church in Montreal, Quebec. Many of his sermons and lectures were published, e.g., "The conquest of Canaan: lectures on the first twelve chapters of the book of Joshua" (1844), "The true gnostics: a sermon preached in Crescent Street Presbyterian Church, Montreal" (1880), "The story of Naaman" (1882), and "A fisherman's folly" (1900).

In 1869, he married Catherine Paterson Craig (1842–1920). He died on July 25, 1901, in Sept Îles, Quebec.