Alexander, born 1875, was the son of Neil MacKillop and Marion MacLeod of Quay, later 11 Borve. He was made a pupil teacher at Berneray School, before travelling around Europe, where he became fluent in French and German, picking up a good knowledge of Italian. In 1917 he married Jean Hogg, with whom he was to have three children. They lived in Edinburgh, where Alexander, who was an excellent Gaelic scholar, became president of Comunn Tir nam Beann.

At the time of his marriage he worked for the Vacuum Oil Company, later becoming an agent, then director of Anglo-American Oil.