Alexander (Sutherland) Sutherland IIIrd of Duffus is a member of Clan Sutherland.
Alexander Sutherland was born c 1400. He was the son of Henry Sutherland, Laird of Torboll & Duffus and his wife Margaret de Moravia.
He married Muriel Chisholm, daughter of John Chisholm and Catherine Bisset, between 19 March 1433 and 1434.
They had 5 known children
Dorothea Sutherland
Muriel Sutherland
Isabella de Sutherland. a 1502
William Sutherland c May 1474
Angus Sutherland
Alexander Sutherland is believed to have died before 1484.
Sources
The family tree of the Dukes, Earls, Lairds and Chiefs of Clan Sutherland 1100-2015 by John M Sutherland-Fisher, Genealogist of Clan Sutherland
The Peerage of Scotland by Sir Robert Douglas (1764) 1st edition within which are found:(Sutherland, Lord Duffus pages 194-196 and Sutherland Earl of Sutherland pages 660-667)
The History of the Earldom of Sutherland by Sir Robert Gordon (written 1650) who was younger son of Alexander Gordon 12th Earl of Sutherland and created 1st Baronet of Gordonstoun
The Sutherland Books Volumes 1-3 by Sir William Fraser (1892) [presented in 1894 by the Duke of Sutherland to Queen Victoria]
A short history of Clan Sutherland , the families of Sutherland, Forse and Duffus 12th -19th centuries by Daniel J J Sutherland, Historian Emeritus of Clan Sutherland. http://www.duffus.com/ashort.htm
A Fighting Clan: Officers in Clan Sutherland 1250-1850 by Malcolm Sutherland, Historian Emeritus of Clan Sutherland.
DNA Connections
It may be possible to confirm family relationships with Alexander by comparing test results with other carriers of his Y-chromosome or his mother's mitochondrial DNA.
Y-chromosome DNA test-takers in his direct paternal line on WikiTree: