A native of Montréal, Stephen Boyd Millen obtained his B.A. and B.C.L. from McGill University, He was called to the Bar of Québec in 1930 and practised with Meredith, Holden, Heward, and Holden from 1930 to 1934. In 1934 he commenced with John Millen and Co., eventually becoming its President and chairman of the Board. Millen served as Governor of McGill University from 1955 to 1958. He also served in a number of other capacities at McGill, including Chairman of the Alma Mater Fund, President of the Montréal Branch of the McGill Graduates' Society, and Chairman of the Athletics Board.

Antonio Milledonne, secretary of the Council of Ten in Venice, was the Republic's observer at the Council of Trent (1545-1563). His account of the Council was never published, though a French translation appeared in Paris in 1870.