Atheling

Malcolm's mother was the sister of the Earl of Northumberland. So the son of Duncan was half-English; and he became more than half-English when, somewhat later, he married Margaret, sister of his friend and guest, "Edgar the Atheling," last claimant of the Saxon throne, who had taken refuge with him while vainly plotting against William the Conqueror.

[…]to substitute as the Confessor′s heir, the Atheling Edward (son of Edmund Ironside), who was then an exile in Hungary. After the atheling′s return from exile, and his very suspicious death in England in 1057, the Norman duke must surely have realized that his chief opponent in England was likely to be Harold Godwineson[…].