In the first third of thirteenth century, the Scottish Crown faced a series of uprisings from the Meic Uilleim, a discontented branch of the Scottish royal family. Ruaidhrí is recorded to have campaigned with Thomas fitz Roland, Earl of Atholl against the Irish in the second decade of the century. One possibility is that these maritime attacks were conducted in the context of suppressing Irish supporters of Scottish malcontents. In 1221/1222, Alexander II, King of Scotland oversaw a series of invasions into Argyll in which Scottish royal authority penetrated into Kintyre. As a result, Ruaidhrí appears to have been ejected from the peninsula and replaced by his younger brother, Domhnall. Whilst Alexander's campaign appears to have been directed at Ruaidhrí, the precise reasons behind it are uncertain. On one hand, the threat of a unified Kingdom of the Isles may have triggered the invasion. On the other hand, if Ruaidhrí had indeed supported the Meic Uilleim, such support to Alexander's rivals could account for royal retaliation directed at Ruaidhrí.
According to several mediaeval chronicles, a certain Roderick took part in the last Meic Uilleim revolt against Alexander. One possibility is that Ruaidhrí and this Roderick are identical. If correct, Ruaidhrí's alliance with the Meic Uilleim may have originated as a consequence of his expulsion from Kintyre by the Scottish Crown. Whilst Ruaidhrí's later descendants certainly held power in the Hebrides and Garmoran, it is uncertain how and when these territories passed into their possession. In 1230, following Scottish interference in the Isles, Hákon Hákonarson, King of Norway sent Óspakr-Hákon to restore authority in the region as King of the Isles. The fact that Ruaidhrí is not recorded in the subsequent Norwegian campaign could be evidence that he had occupied himself in supporting the near-concurrent Meic Uilleim rebellion, or that he resented the prospect of Óspakr-Hákon's overlordship.
Ruaidhrí seems to be identical to a certain Mac Somhairle who was slain in battle assisting Maol Seachlainn Ó Domhnaill, King of Tír Chonaill resist an English invasion. The following year, Ruaidhrí's son, Dubhghall, and another Clann Somhairle dynast sought the kingship of the Isles from Hákon. There is reason to suspect that Mac Somhairle had previously been recognised by Hákon as King of the Isles, and that the two Clann Somhairle kinsmen sought to succeed Mac Somhairle as king after his death. Whatever the case, Ruaidhrí's sons were certainly active in Ireland afterwards, with his younger son, Ailéan, being one of the earliest gallowglass commanders on record.
Ruaidhrí seems to have been the senior son of Raghnall mac Somhairle (died 1191/1192–c.1210/1227). Raghnall was in turn a son of Somhairle mac Giolla Brighde, King of the Isles (died 1164), the common ancestor of Clann Somhairle. Another son of Somhairle was Dubhghall (died 1175×), eponymous ancestor of Clann Dubhghaill. Ruaidhrí was in turn the eponymous ancestor of Clann Ruaidhrí, whilst his brother, Domhnall, was the eponym of Clann Domhnaill.
There is uncertainty regarding the succession of the Clann Somhairle leadership following Somhairle's death in 1164. Although the thirteenth–fourteenth-century Chronicle of Mann reports that Dubhghall was the senior dynast in the 1150s, this man's next and last attestation, preserved by the Durham Liber vitae, fails to accord him a royal title. One possibility is that Dubhghall had been succeeded or supplanted by Raghnall, whose recorded title of rex insularum, dominus de Ergile et Kyntyre ("king of the Isles, lord of Argyll and Kintyre") could indicate that Raghnall claimed control over the Clann Somhairle territories. Like Dubhghall, the year and circumstances of Raghnall's death are uncertain as surviving contemporary sources fail to mark his demise.