Born at Burnside Hall, Montreal, Strachan Bethune was the son of the Very Reverend John Bethune, Dean of Montreal and Principal of McGill University, by his wife Elizabeth, daughter of William Hallowell (1771–1838), signing partner of the North West Company.

He was named for his father's mentor John Strachan, and he was a great-grandson of the explorer Alexander Henry the elder.

He was twice appointed Bâtonnier of Montreal (1859 and 1862) and his name was frequently mentioned when judicial vacancies became available.

[1] In 1845, by his father at Christ Church Cathedral, Montreal, he married Maria MacLean Phillips (1826–1901), the eldest daughter of William Phillips of Quebec City, by his wife Henrietta, daughter of Charles Grey Stewart (1775–1854), of Quebec.

Their second daughter, Caroline, married Lt.-Col. Hon Keith Turnour-Fetherstonhaugh of Uppark, younger brother of Edward Turnour, 5th Earl Winterton.