Died after 1448 according to The Scots Peerage, Vol. VIII, edited by Sir James Balfour Paul, p. 331.

Nicolas, named by the Earl in a charter of May 1448 as his son.[9]

[9] Sutherland Book, 26, 27.

http://www.archive.org/stream/heraldryofmurray00john#page/4/mode/2up Page 5 No. 20-c

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
• 2a JOHN, 8th Earl

* 3a Nicholas, living 1448

• 4a Thomas Beg (‘The Little'); allegedly ancestor of the SUTHERLANDs OF STRATHALLIE
• 5a Robert, living 1487
• 1a Janet; married Alexander Dunbar, 3rd son of Sir Alexander Dunbar of Westfield (see DUNBAR OF MOCHRUM, Bt), and had issue