According to the 19th century Clan Donald historians Angus and Archibald Macdonald, Alasdair Mór must have been a prominent man as he is the only recorded brother of Aonghus Mór.
[1] In that year he was slain in a conflict with Alasdair of Argyll and the MacDougalls.
[2] He is said to have had at least five sons: Dòmhnall, Gòraidh, Donnchadh, Eoin and Eachann.
Alasdair Mòr was succeeded in the representation of his clan by Dòmhnall.
[3] Today he is considered to be the eponymous ancestor of Clan MacAlister.