Alan Dower Blumlein was born on 29 June 1903 in Hampstead, London. His father, Semmy Blumlein, was a German-born naturalised British subject. Semmy was the son of Joseph Blumlein, a German of Jewish descent, and Philippine Hellmann, a French woman of German descent. Alan's mother, Jessie Dower, was Scottish, daughter of William Dower (born 1837) who went to South Africa for the London Missionary Society. Alan was christened as a Presbyterian; he later married in a Church of England parish church.