Alexander Stewart (c. 1493 – 9 September 1513) was an illegitimate son of King James IV of Scotland by his mistress Marion Boyd. He was the King's eldest illegitimate child. He was an elder brother of Catherine Stewart his only full sibling, a half brother to James Stewart, Margaret Stewart and Janet Stewart, the other illegitimate children of James IV and his mistresses. He was an older half-brother of the future James V.
Alexander Stewart's mother was Marion Boyd, daughter of Archibald Boyd of Bonshaw, whose sister Elizabeth Boyd was married to Archibald Douglas, 5th Earl of Angus. Douglas, who served as Lord Chancellor of Scotland between 1493 and 1498, encouraged the relationship between his niece Marion and the young King James IV. James's children by Marion Boyd were Alexander, born c. 1493, and Catherine Stewart. Catherine (d. after 1554) married James Douglas, 3rd Earl of Morton (d. 1548).
From a young age Alexander was groomed for a life in the church. At the age of four his father received a dispensation from illegitimacy by Julius II enabling him to join the church. By September 1502 he was archdeacon, when his uncle James, Duke of Ross died in 1504 his father the King nominated him as the new Archbishop of St Andrews. Alexander was still only a boy at age 11 which would mean his father could still receive the revenues of St Andrews since Alexander was under age until he turned 27.
He received a superb education firstly from James Watson, later Dean of the Arts faculty at St Andrews, and latterly from Patrick Paniter whom he seemed to have been close to. In 1507 Alexander Stewart was sent to France on the royal ship the Treasurer. His education continued with lengthy journeys to the Low Countries, and Italy in 1507. In Padua he studied rhetoric and Greek under Erasmus who wrote a moving obituary after young Alexander’s death at the Battle of Flodden. Erasmus mentioned their time at Siena where after studies in the morning Alexander would play the monochord, recorder or lute in the afternoon. Alexander returned to Scotland in 1510 and at the age of 17 became Lord Chancellor of Scotland.