 He was born in London, England on November 15, 1857, the son of Lt. Col. James Fielding Sweeny, formerly Her Majesty's staff officer of pensioners at Montreal, and his wife, Anna Maria Fielding.Sweeny was one of ten children, and his brothers included George Robert Sweeny, a barrister of Toronto, Charles Sweeny, a Vice President of the CPR, and Roger Sweeny, Commandant of Her Majesty's Indian Army Staff College, and sisters Kathleen Chipman and Georgina, Lady Alymer, wife of Arthur Lovell Aylmer, Lord Aylmer.He was educated at the High School of Montreal, at McGill Normal School, and at McGill University (B.A., 1878 ; M.A.