Duncan, born 1771, was the son of Alexander MacLeod, Alasdair Ruadh. Duncan, who came from Scarista, married Mary MacLeod, with whom he had at least five children. They lived in Ruisgarry, where in 1830 Duncan was paying annual rent of £5.

Given his name, Duncan could possibly be associated with Tobhta nan Gillean Ruaidhe, on the northern coast of Ruisgarry.