Born in Melbourne, Canada East, the son of Udolphus Aylmer, 7th Baron Aylmer and Mary Journeaux, Aylmer was educated at the High School of Montreal and the Royal Naval College in Portsmouth, England. He served in the Canadian militia during the Fenian raids and was a lieutenant in the Royal Marine Artillery. He organized the Richmond Field Battery in 1876 and held command until November 1887, when he retired with rank of lieutenant-colonel.