Little is known of James's life before the arrest of his father, the Duke of Albany, and his eldest son Alexander, for treason by King James I of Scotland on 21 March 1425, on the 9th day of the March parliament. The family properties of Doune Castle and Falkland Palace were captured, and Duke Murdoch and two of his sons were imprisoned and held pending trial. James soon became a rallying point for enemies of the King, raising a large rebellion against the crown. Initially at least, events moved in his favour. He received the support of his mother's supporters in the Lennox, and also from Fionnlagh MacCailein, Bishop of Argyll, a long-standing supporter of the Albany Stewarts. James marched on the town of Dumbarton, burned it, and killed the keeper of the royal castle there, Sir John Stewart of Dundonald, who was the King's uncle. However, the castle itself, commanded by John Colquhoun, successfully held out against James's men. Among other supporters were the Clan Galbraith, in particular the ninth chief James Galbraith of Culcreuch who joined Stewart's rebellion. As many as 600 members of the clan were forced to flee after the failure of the revolt, exiled to Kintyre and the Isle of Gigha, where they adopted the new name of MacBhreatneaich of M'Vretny .
Escape to Ireland
James the Fat's rebellion was quickly defeated. His father and brothers were found guilty of treason by a jury of knights and peers, and executed after a trial. At a stroke, almost all of James' family was wiped out. Only his mother, Isabella of Lennox survived the insurrection. Later in 1425, pursued by a royal expedition, James fled to Antrim, Ireland, accompanied by the illegitimate sons of his dead brother Walter of Lennox, to escape the King's justice. Few details of his escape survive but it seems likely that he sought assistance from the Campbells of Lochawe, to whom he was closely linked by blood and marriage. James the Fat would never return to his native Scotland. He remained an exile in Ireland until his death. His widowed mother and sister remained in Scotland.
Claim to the throne
James Stewart was in line to claim the throne as sole surviving grandson of the Duke of Albany, brother to the late King Robert III.
James "Beg" Stewart was able to secure a royal pardon and return to Scotland. He married Annabel Buchanan, daughter of Patrick, 14th Lord of Buchanan, and was granted the estate "Baldorran" from his cousin John Stewart Damby in 1457. He is the ancestor of the Stewarts of Ardvorlich on Lochearnside, whose family history is recounted by Sir Walter Scott in A Legend of Montrose.
Alexander Stewart, born c.1437 in Antrim, Ireland.
James' mother Isabella of Lennox was imprisoned by King James in Tantallon Castle after the execution of her husband and children. However, in 1437 the King was himself assassinated, and soon afterwards Isabella was released from captivity, eventually recovering her lands and title. In the next few years, although forced to govern her province from her castle at Inchmurrin, Loch Lomond, she issued a large numbers of charters, was popular in the province, and was tolerated by King James II. At some point after she regained her liberty, Isabella brought her young grandchildren, the children of James the Fat, to be raised at her castle at Inchmurrin.
