The Black Knight of Lorne was born at Innermeath, Scotland. His father was Sir John Stewart (died 26 April 1421), Scotland's Ambassador to England. He was a direct male line descendant of Alexander Stewart, 4th High Steward of Scotland, through his second son Sir John Stewart of Bonkill, who was killed at the Battle of Falkirk. His mother was also a descendant of Elizabeth de Burgh, second wife/Queen Consort of King Robert I ("The Bruce").