According to Foras Feasa ar Éirinn, Cathaoir Mor was a son of Feidhlimidh Fiorurghlas, son of Cormac Gealta Gaoth, son of Nia Corb, son of Cu Corb, son of Mogh Corb, son of Conchubhar Abhradhruadh, son of Fionn File, son of Rossa Ruadh, son of Fearghus Fairrge, son of Nuadha Neacht, son of Seadna Siothbhac, son of Lughaidh Loithfhionn, son of Breasal Breac, son of Fiachaidh Foibhric, son of Oilill Glas, son of Fearadhach Foghlas, son of Nuadha Fullon, son of Ealloit, son of Art, son of Mogh Airt, son of Criomhthann Coscrach, son of Feidhlimidh Foirthriun, son of Fearghus Fortamhail, son of Breasal Breodhamhan, son of Aonghus Ollamh, son of Oilill Bracain, son of Labhraidh Loingseach of the race of Eireamhon.[2]
Legends
He is said to have had thirty sons, but only ten of them had children; several medieval dynasties of Leinster traced their ancestors to them.[5][6] His daughter Cochrann was said to have been the mother of the fenian hero Diarmuid Ua Duibhne.[7]
He features in the saga Esnada Tige Buchet ("The Melody of the House of Buchet"). Cathair's daughter Eithne Tháebfhota is fostered by a hospitable Leinsterman named Buchet who has many herds of cattle, but Cathair's sons so exploit Buchet's hospitality that he is left with only one bull and seven cows, and the king, now old and enfeebled, is unable to restrain them. Buchet and his family, including Eithne, are reduced to living in a hut in the forest in Kells, County Meath. Later, when Cormac mac Airt is king, he marries Eithne and restores Buchet's fortunes[8] (in other stories the king who marries Eithne is Cathair's successor Conn Cétchathach).[9] In another saga, Fotha Catha Cnucha ("The Cause of the Battle of Cnucha"), Cathair gives the hill of Almu (Knockaulin, County Kildare) to the druid Nuada son of Aichi. This hill will later be famous as the home of Nuada's great-grandson Fionn mac Cumhaill.[10]
^On the page of this book, the author wrote that Sodhealbh and her sister, Eithne, were the daughters of Baite, Cathair Mor don't be her father. But later on the book mentioned Sodhealbh as Cathair Mor's daughter and Oilill Olum's wife, probably a mistake of this author. Oilill Olum married Sadb, daughter of Eithne, another daughter of Cathair Mor.