About Alexander Sutherland
Alexander, Master of Sutherland, who is named as such in a charter by Alexander, Earl of Ross, granted at Inverness 10 October 1444. It is apparently he who is named in the safe-conduct of 3 February 1444-45, already cited, but he must have died before February 1455-56, when his father resigned the earldom to his brother John.
 Sutherland Book, iii. 28-32.
http://www.archive.org/stream/heraldryofmurray00john#page/4/mode/2up Page 5 No. 20 - a
20(a) Alexander, Master of Sutherland, died v.p. and s.p. before 1456.
Burke's Peerage entry -
JOHN SUTHERLAND, 7th Earl of Sutherland; born c 1390; knighted 1408; married by 1342 Margaret (died 1510), a famous beauty, daughter of Sir William Baillie of Lamington, and had:
1a Alexander, Master of Sutherland; died in the lifetime of the father by 22 Feb 1455/6