He was born on 8 September 1912 the only child of Francis and Martha Mackendrick who had emigrated to the United States from Glasgow in 1911. His father was a ship builder and a civil engineer. When Mackendrick was six, his father died of influenza as a result of a pandemic that swept the world just after World War I. His mother, in desperate need of work, decided to be a dress designer. In order to pursue that decision, it was necessary for Martha MacKendrick to hand her only son over to his grandfather, who took young MacKendrick back to Scotland when he was seven years old. Mackendrick never saw or heard from his mother again.