Question: Who is Domhnall Mac Alasdair's paternal grandfather?

Knowledge 1: Domhnall mac Alasdair
Domhnall mac Alasdair was a son of Alasdair Mór mac Domhnaill, and a member of Clann Domhnaill.Domhnall is attested by the fifteenth-century manuscript National Library of Scotland Advocates' 72.1.1 (also known as 1467 MS and 1450 MS).He may be identical to Domhnall of Islay.The latter's attestations suggest that he was a contestant to the Clann Domhnaill lordship, and may have possessed the chiefship. [SEP] Knowledge 2: Alasdair Mór
Alasdair Mór mac Domhnaill was a younger son of Domhnall mac Raghnaill—the eponymous ancestor of Clan Donald.He first appears on record in 1253, when it is recorded as witnessing a charter by his brother, Aonghus Mór, to Paisley Abbey.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.He is recorded in the Annals of Connacht, in the year 1299, as being a man noted for being a "generous and bounteous man".In that year he was slain in a conflict with Alasdair of Argyll and the MacDougalls.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.Today he is considered to be the eponymous ancestor of Clan MacAlister.
Knowledge 1: Domhnall mac Alasdair
Domhnall mac Alasdair was a son of Alasdair Mór mac Domhnaill, and a member of Clann Domhnaill.Domhnall is attested by the fifteenth-century manuscript National Library of Scotland Advocates' 72.1.1 (also known as 1467 MS and 1450 MS).He may be identical to Domhnall of Islay.The latter's attestations suggest that he was a contestant to the Clann Domhnaill lordship, and may have possessed the chiefship. [SEP] Knowledge 2: Gilbert de Insula
Gilbert de Insula (Anglicised: "Gilbert of the Isles") was a son of Domhnall mac Alasdair, who received a charter for unspecified lands in the Stirlingshire region, in the year 1330.He also received a charter for half the lands of Glorat in the parish of Campsie.Today, Gilbert de Insula is considered to be a grandson of Alasdair Mór.He is also considered to possibly be the ancestor of the Alexanders of Menstrie.
Knowledge 1: Alasdair Mór
Alasdair Mór mac Domhnaill was a younger son of Domhnall mac Raghnaill—the eponymous ancestor of Clan Donald.He first appears on record in 1253, when it is recorded as witnessing a charter by his brother, Aonghus Mór, to Paisley Abbey.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.He is recorded in the Annals of Connacht, in the year 1299, as being a man noted for being a "generous and bounteous man".In that year he was slain in a conflict with Alasdair of Argyll and the MacDougalls.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.Today he is considered to be the eponymous ancestor of Clan MacAlister. [SEP] Knowledge 2: Gilbert de Insula
Gilbert de Insula (Anglicised: "Gilbert of the Isles") was a son of Domhnall mac Alasdair, who received a charter for unspecified lands in the Stirlingshire region, in the year 1330.He also received a charter for half the lands of Glorat in the parish of Campsie.Today, Gilbert de Insula is considered to be a grandson of Alasdair Mór.He is also considered to possibly be the ancestor of the Alexanders of Menstrie.

Answer: Domhnall mac Raghnaill