As the eponymous ancestor of the Uí Failge, he may be the son of the high king of Ireland, Cathair Mór, said to have lived in the early 2 cd century. This is the ancestor listed in the genealogies, though chronologically impossible.Byrne, Table 8; Charles-Edwards, Appendix XV The Book of Leinster king list names an early king Failge Rot mac Cathair. The Uí Failge appear to have had an early leadership among the Laigin tribes. This is testified by the early Irish poem Timna Cathaír Máir ("The Testament of Cathair Mór) where Rus Failge is given the succession to his father.Byrne, pg.139
