Dictionary of National Biography, 1885-1900/Mar, William
MAR, WILLIAM, ninth Earl of (d. 1281?), was the son of Duncan, eighth earl of Mar, and grandson of Morgrund, fifth earl. He succeeded his fat her in or before 1237, when he attested at York the agreement between Henry III of England and Alexander II of Scotland. His right of succession was contested by Alan Durward, who asserted that William's father and grandfather were both of illegitimate birth, and that he ought to succeed as lawful heir. But apparently the case was arranged on the footing of an agreement which had been made about 1228 with Thomas Durward, father of Alan, who received a large accession of territory in Mar ; and the earldom remained with William de Mar. In 1249, during the minority of Alexander III, he was appointed one of the regents of Scotland. He held the office of great chamberlain of Scotland from 1252 to 1255, in which year, owing to political dissensions, he was removed from the government, and received permission from Henry to sojourn for a time in England. In 1258 he was a party to the treaty between some of the Scots and Llewellyn, prince of Wales, not to make peace with Henry without each other's consent (Rymer, Fœdera, i. 370). But in the same year he was reappointed one of the Scottish regents, and they received the promise of Henry's support so long as they acted righteously. He again became great chamberlain of Scotland in 1262, and continued in the office till 1267. He was also sheriff of Dumbartonshire. After the battle of Largs in 1263 he was sent by Alexander III with a military force to reduce the chiefs of the Western Isles who had supported Haco, king of Norway. He was still alive in 1273, but must have died in or before 1281. He married Elizabeth, daughter of William Comyn, earl of Buchan, by whom he had two 'sons, Donald, tenth earl [q. v.], who succeeded, and Duncan; and after her death he married an English lady, Muriel, granddaughter and one of the heiresses of Robert de Muschaump, whose barony lay in the see of Durham, but had no issue by her. She died in 1291 (Raine, North Durham, p. 267).
[Bain's Calendar of Documents relating to Scotland, vol. i. passim, vol. ii. Nos. 201, 477, 544 ; Antiquities of Aberdeenshire, vols. i-iv. passim ; Exchequer Rolls of Scotland, i. lxv, 10, 11, 30, ii. cxxi; Kymer's Fcedera, i. 329, 353, 378, 402.]