The title Earl of Morton was created in the Peerage of Scotland in 1458 for James Douglas. Along with it, the title Lord Aberdour was granted. This latter title is the courtesy title for the eldest son and heir to the Earl of Morton.
One of his dependants, Captain James Stuart, son of Lord Ochiltree and brother-in-law of Knox, had the daring to accuse Morton at a meeting of the council in Holyrood of complicity in the murder of Darnley, and he was at once committed to custody.
In 1586, however, the attainder was rescinded in favour of Archibald Douglas, 8th Earl of Angus, a nephew of the 4th earl.
Archibald Douglas, 8th Earl of Angus, and Earl of Morton (1555-1588), was the son of David, 7th earl.