Alexander Howard MacKay was born on May 19, 1848, in Plainfield, Pictou County, Nova Scotia.

He was an educator and scientist. He attended the Pictou Academy (1865) and graduated from Dalhousie University in Halifax (B.A., 1873; B.Sc., 1880). In 1873, he started as principal of the Annapolis Academy, but soon after he returned to the Pictou Academy to begin a 16-year career as a principal. There he strengthened the science program, organized the Pictou Academy Scientific Association, and pursued his own botanical and zoological research. In 1889, he became principal of the Halifax Academy. He was active in the Provincial Educational Association of Nova Scotia, founded the Summer School of Science for teachers in 1887, and served as Nova Scotia editor of the Educational Review (Saint John) (1887-1891). In 1891, MacKay began a 35-year term as superintendent of education for Nova Scotia, constantly urging the provincial Council of Public Instruction and local school trustees to reform the curriculum and to hire trained teachers. Throughout his life, he continued his scientific studies, his work on the flora and fauna of his own province, and developed a herbarium of native plants. From about 1908 until his death he edited the Proceedings and Transactions of the Nova Scotian Institute of Science, of which he was president from 1899 to 1902. He was president of the Dominion Educational Association (1895-1898) and in 1909, he became vice-president of the Simplified Spelling Board of New York. He served on the board of governors of Dalhousie (1888-1927) and he represented the university on the board of the Marine Biological Stations of Canada (1898-1926). He was awarded an honorary doctorate by Dalhousie in 1892 and by St. Francis Xavier College, Antigonish, in 1905. He was a director or board member of the Presbyterian College, the Halifax Ladies’ College, and the Victoria School of Art and Design, where he served as president from 1908 to 1924. Active in the North British Society, of which he was president in 1894, he served as vice-president of the Nova Scotia Historical Society from 1896 to 1902 and as president of the Halifax Canadian Club in 1912–1913.

In 1880, he married Maude Augusta Johnston (1851–1936). He died on May 19, 1929, in Dartmouth, Halifax, Nova Scotia.

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.

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)

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