Henry "Harry" Poole MacKeen was born in Glace Bay, Nova Scotia on 17 June 1892, the son of David MacKeen, former Lieutenant Governor of Nova Scotia (1915-1916), and Jane Kate (Crerar) MacKeen. He was educated at St. Andrew's College in Toronto and graduated from McGill University with a BA in 1914. He served during World War I as an artillery officer, rising from the rank of lieutenant to major. He completed his BCL at McGill in 1920 and received his LL.B. from Dalhousie University in 1921. Thereafter, he practiced law with Stewart, Smith, and MacKeen in Halifax, starting that same year. On 6 October 1928 he married Alice Richardson Tilly, daughter of former New Brunswick Premier Leonard Percy de Wolfe Tilley in Saint John, New Brunswick. He also served with the 2nd Battalion, Halifax Rifles, during World War II and rose to the rank of lieutenant-colonel by 1945. He acted as the Honorary Lieutenant Colonel of the battalion from 1948 to 1960. He was a director of the Nova Scotia Trust Company, Point Pleasant Park, Atlantic Building Materials Ltd., Consulting Ed., and the Canadian Encyclopedic Digest. He served on the Board of Governors of the Federation of Insurance Counsel, 1960-1963. He also served as president of the Nova Scotia Barristers' Society, which made him an honorary president in 1960 and honorary life member in 1966; and as a vice-president of the Canadian Bar Association. In 1963 he was appointed the 22nd Lieutenant Governor of Nova Scotia since Confederation. He served in that capacity until 1968. Thereafter, he was appointed the first Chancellor of Acadia University in 1969. That same year he received the Medal of Service from the Order of Canada. He died on 20 April 1971.

Alice Richardson (Tilley) MacKeen was born in Saint John, New Brunswick on 11 August 1904, the daughter of former New Brunswick Premier, Leonard Percy de Wolfe Tilley and Laura Tremaine (Richardson) Tilley. She was also the granddaughter of Samuel Tilley, one of the Fathers of Confederation. On 6 October 1928 she married Henry Poole MacKeen, son of former Nova Scotia Lieutenant Governor, David MacKeen in Saint John, New Brunswick. In 1936 Alice was badly burned during a Halifax Harbour boating accident after she was trapped in the flames near the bow of the vessel. In 1963 her husband was appointed the 22nd Lieutenant Governor of Nova Scotia since Confederation and served in that capacity until 1968. She died in Halifax, Nova Scotia on 14 July 1996.