He was the son of the high king Áed Sláine mac Diarmato (died 604).
He was contemporary to his brother Congal mac Áedo Sláine, who was called King of Brega in the annals, whereas Ailill was not.
[2] The annals mention that in 634 Ailill and his brother Congal were defeated and slain at the Battle of Loch Trethin at Fremainn (Loch Drethin at Frewin Hill, County Westmeath) by the same Conall Guthbinn of the Clann Cholmáin who had slain their father.
[4] Ailill's son Dlúthach was ancestor of the Síl nDlúthaig sept, or as Fir Cúl Breg, men of the churches of Brega.
His grandson Áed mac Dlúthaig (died 701) was a king of Fir Cúl.