 At Robert III's accession, his heir apparent was his eldest son
Robert III died on 4 April 1406, allegedly of grief at his son's capture, and was succeeded as King by his only surviving son James (a second son, Robert, had died young).The new eleven-year-old King had several sisters living, but under the 1371 Act of Parliament limiting the succession to males his heir presumptive was his uncle
King James I was assassinated on 21 February 1437 by a group of conspirators including his uncle and sometime ally the Earl of Atholl, whereupon his infant son became King as James II.At the accession of James II the next male heir to the Crown was the late King's assassin 
The only other unquestionably legitimate male member of the House of Stewart apart from the King was now Sir James "Mór" Stewart of Baldorran, son of the second Duke of Albany, who was in exile in Ireland.