Dictionary of National Biography, 1885-1900/Mar, Donald (d.1297)
MAR, DONALD, tenth Earl of (d. 1297), was the son of William, ninth earl [q. v.], and Elizabeth Comyn, his first wife. He was knighted by Alexander III at Scone in 1270, and succeeded as earl before 25 July 1281, when he took oath at Roxburgh to observe the treaty for the marriage of Princess Margaret of Scotland and Eric, king of Norway. At Scone in 1284 he similarly undertook to acknowledge their daughter, the Maid of Norway, as queen of Scotland in the event of Alexander's death, and in 1289 he united with the community of Scotland in recommending to Edward I of England the marriage of the Prince of Wales and the Maid of Norway. This was agreed to, and the marriage arranged at Birgham, Berwickshire, in July 1290, in a treaty to which Mar was a party. After the death of the Maid of Norway, when different claimants appeared for the Scottish crown, Mar united in the Scots' appeal to Edward to be their arbiter. Personally he supported the claim of Robert Bruce, whose son, the future king, married his daughter Isabel, and whose daughter,Christian, married his son, Gratney. He swore allegiance to Edward at Upsettington, Berwickshire, on 13 June 1291, and was a witness to Edward's protest at Berwick as to his claim to be lord superior of Scotland. Under Edward's suzerainty he held the office of bailie of Aboyne. In 1294 Mar, with other Scottish nobles, was summoned to London to attend Edward on foreign service. Rather than obey they revolted. But after the battle of Dunbar, in 1296, Mar came to Edward at Montrose, and afterwards swore fealty again at Berwick. He was, notwithstanding, carried prisoner to England, but was released on parole, 23 June 1297, in order to visit Scotland, Edward at the same time exacting from him a pledge that he would serve him against France. He died about this time, leaving a son and successor, Gratney, eleventh earl of Mar, and father of Donald, twelfth earl of Mar [q. v.]; he also left two daughters, Isabel, wife of Robert the Bruce, and Mary, who married Kenneth, earl of Sutherland.
[Bain's Calendar of Documents relating to Scotland, vol. ii. passim; Antiquities of Aberdeenshire (Spalding Club), iv. 198, 600, 698-704; Rymer's Fœdera, i. 596, 638, 730-74, 791, 804.]