Ailéan was a brother of Dubhghall mac Ruaidhrí, King of Argyll and the Isles, a significant figure who held power in the mid thirteenth century.

In 1259, Dubhghall's daughter married the son of King of Connacht, and Ailéan is recorded to have commanded the woman's tocher of one hundred and sixty gallowglass warriors.

The record of his part in the ruthless suppression of a Manx revolt in 1275, and his participation in a parliamentary council concerning the inheritance of Scottish throne in 1284, both evidence the incorporation of Clann Somhairle into the kingdom.

For example, the northern Hebridean islands of Lewis and Harris and Skye appear to have been held by the Crovan dynasty, then represented by the reigning Haraldr Óláfsson, King of Mann and the Isles.

[29] It is conceivable that Eóghan and Dubhghall sought kingship over the same jurisdiction that Hákon had awarded to Óspakr-Hákon about a decade before—a region which could have included some or all of the islands possessed by Clann Somhairle.

[37] Although the Scottish Crown appears to have attempted to purchase the Isles earlier that decade,[38] Eóghan's acceptance of Hákon's commission partly led Alexander II, King of Scotland to unleash an invasion of Argyll in the summer of 1249, directed at the very heart of the Clann Dubhghaill lordship.

[53][note 4] The marital alliance was conducted at the main port within Brian's realm, a site indicating that the union—along with the aforesaid assembly and naval operations of the previous year—was part of a carefully coordinated plan to tackle English power in the north west of Ireland.

[63] The Clann Ruaidhrí dowry of these warriors may well have fought at the aforesaid battle at Downpatrick,[64] although the fact that Brian's forces were defeated by local English levies lends little evidence to their capabilities.

[68] In 1262, the year after yet another failed attempt by the Scottish Crown to purchase the Isles, the thirteenth-century Hákonar saga Hákonarsonar reports that the Scots lashed out against the Islesmen in a particularly savage attack upon the inhabitants of Skye.

[69] Thus provoked, Hákon assembled an enormous fleet—described by the Icelandic annals as the largest force to have ever set sail from Norway[70]—to reassert Norwegian sovereignty along the north and western coast of Scotland.

[71][note 5] In July 1263, this armada disembarked from Norway, and by mid August, Hákon reaffirmed his overlordship in Shetland and Orkney, forced the submission of Caithness, and arrived in the Hebrides.

[75] When negotiations between the Scottish and Norwegian administrations broke down, the saga identifies Magnús Óláfsson, King of Mann and the Isles, Dubhghall, Ailéan, Aonghus Mór Mac Domhnaill, and Murchadh Mac Suibhne, as the commanders of a detachment of Islesmen and Norwegians who entered Loch Long, portaged across land into Loch Lomond, and ravaged the surrounding region of the Lennox.

[93] Not only did Hákon fail to break Scottish power, but Alexander III seized the initiative the following year, and oversaw a series of invasions into the Isles and northern Scotland.

Recognising this dramatic shift in royal authority, Magnús Óláfsson submitted to Alexander III within the year,[94] and in so doing, symbolised the complete collapse of Norwegian sovereignty in the Isles.

Specifically, with the conclusion of the Treaty of Perth in July, Hákon's son and successor, Magnús Hákonarson, King of Norway, formally resigned all rights to Mann and the islands on the western coast of Scotland.

[102] Alexander III responded by sending a massive fleet, drawn from the Hebrides and Galloway, to invade the island and restore Scottish royal authority.

Of the recorded commanders, the continuation of Historia rerum Anglicarum reveals that two were members of Clann Somhairle: Alasdair Mac Dubhghaill, Lord of Argyll, and Ailéan himself.

[111] For instance, in 1284, Ailéan was one of the many such men who attended a government council at Scone which acknowledged Margaret, granddaughter of Alexander III, as the king's rightful heir.

[122] On the other hand, the family's position in the Isles may have stemmed from its marital alliance with the Crovan dynasty, an affiliation undertaken at some point before Ruaidhrí's apparent expulsion from Kintyre.