 Fiachra Cossalach was a son of Dúngal Eilni mac Scandail (died 681) and hence a member of the Eilne branch of the family.In the "Annals of Ulster" he is referred to as the son of Dúngal in his death notice in the annals.Curiously, Fiachra is mentioned as one of the guarantors of the Cáin Adomnáin at the Synod of Birr in 697 as king of the Cruithin at a time when Áed Aired (died 698) was considered to be king.