Leabhar Clainne Suibhne (The Book of Mac Sween) states that after Áed's death, although his older brother Domnall was the rightful heir, Ánrothán was chosen instead to be king. Ánrothán then gave up the kingship to his brother and made for Argyll, Scotland where he married a daughter of the King of Scotland. Ánrothán's great-grandson was Suibne, from whom the clan derived its name.
The history from Leabhar Clainne Suibhne may be a fabrication that provides the clan with a pedigree connecting them to the Milesian kings of Ireland, although historian W. D. H. Sellar believes this history may be genuine.
Read more about this topic: Clan Sweeney