Ó Catháin of Ulster Pedigree-

NIALL Noigallach ("Neill of the Nine Hostages"), Ard Ri 379-405 AD. Married Ine, daughter od Dubhtach, king of Ulster. 

EOGAIN, King of Ailech 425-465, which he founded when he captured the prehistoric drystone ring fort on Grianan Mountain, Co Donegal. Married Indorb Finn. 

MUIREADACH, King of Ailech 465-480, eloped with Erca, daughter of Loarn, king of the Scots in Airer Gaedhill (Argyll). 

MUIRCEARTAIGH I, King of Ailech 513-533 and Ard Ri, married Duaibhsech, daughter of Duach Teangumha, King of Connachta.
 
DOHMNAILL I Ilcealccaigh (Donnell the Deceitful"), King of Ailech565-566 and Ard Ri

AEDH IV Uairiodhnaigh ("Hugh of the Ague"), King of Ailech 605-612, benefactor of his cousin, St Mura. 

MAEL FITHRIGH ('governor, fierce king'), King of Ailech 628-630

MAEL DUIN 'governor of the fort'), King of Ailech 671-681. Married Cacht, daughterbof Maaelcobha, king of Tir Conail. 

FEARGHAIL ("man of valour"), King of Ailech 710-722, Ard Ri 711-722. Married Athirocht, daughter of Cian, king of Ciannachta.

CONCOBHAIR ('warrior aid"), Prince of the Royal House of U Niall, brother to the Ui Niall king. Connor's inheritance was Moy Ith, the root of the Inisowen Peninsula. Died 773 AD. 

GRUAGAIN ("hairy man, giant, magician, hero")

DUNGAN ('destroying")

CATHAIN ("warrior"), living about 950. The Annals of Ulster record: MacCathain (i.e. son of Cathain) fell asleep in Christ, 944 AD. 

CATHASAIGH (Gaelic: Cath - Battle; ?-saighead - Arrow), b. ca. 990, ancestor of O'Cahan (Ó Catháin)  m. ca. 1020 (O'Lunnin MS) Doubhcoubhla, daughter of Donnchad (Mor), King of Munster, (d. 1065)son of King Brian 'Boru' (as above), and had issue,

DERMOD, b. ca. 1020, m. (O'Lunnin MS) Elinor, dau. of Macgenis, Lord of Tiragh, and had issue,

CONN CIONNTACH Ó Catháin (or "Conkenny" in O'Lunnin MS), first to assume the surname,  from O'Lunnin MS, he m. "Rose, dau. of Hugh Boye, First Lord of Clannaboye in the County of Antrim" (Note: appears anachronistic - Hugh lived in mid-13th C. - but possibly an earlier ancestor), and had issue,

GIOLLCHRIOSD Ó Catháin, b. ca. 1065, m. (O'Lunnin MS) Mary, dau. of Hugh McMahon, Lord of Monaghan, and had issue,

IOMHAR Ó Catháin, b. ca. 1085, m. (O'Lunnin MS) Winifred, dau. of Gilliosa O'Reilly, Lord of Cavan, and had issue,

RANNALL Ó Catháin, b. ca. 1105, Chief of his Name; the first of the family to be mentioned in the Annals of Ulster (AU-1138), by which date he was "Lord of The Craebh (Creeve), Ciannachta and Fir Li"; having conquered the Ciannachta in the territory around Dungiven, Co. Derry; m. (O'Lunnin MS) Honora, dau. of Roarke, "Prince of Bressic (sic ?-Breffny), containing three counties, viz. Leitrim, Cavan and Fermanagh"; k. 1138, having had issue.


Ó Catháin of Galway Pedigree- 

This pedigree is incomplete, as are many pedigrees. It appears that what became the Ó Catháin of Cenel Ianna started out as the Tradraige, who were one of the Saortuatha Eoghanachta Mumha or nobility of the Eoganacht of Munster. The Ó Catháins of Cenel Ianna are haplogroup R-DF21 as are the McCarthy kings of Munster, albeit a different sub-clade. When the kingdom of Tradraige was threatened, a local abbot appealed to Felimy, king of Munster, asking for his aid against the opression of the Corcabaskin, on the grounds of the Tradraige being Saorclanna Eoghanachta. 

Trad MacTaoiseach, son of a chief and druid, king of Tradraige, Co Clare. Married Aoife, daughter of Lughaidh Delbaeth and left Bruree, Co Limerick, to become chief of Tradraige, a composite kingdom with his mother's people, the Dealbhna, yet another haplogroup R-DF21 sub-clade. Aoife's brother Aedhan, was ancestor of the Dealbhna. 
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Con Bearnach, ca.500. Con appears to have been tacked onto the pedigree of the Tradraige's new dynasty, the Ui Fiachra Aidhne. 
Concobhair Floinn
Ailgenaigh
Ionnach,a quo Cenel Ianna. Ionnach's brother Tadhg was ancestor of O'Mochain, which clan bears another Df21 sub-clade.  
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Catháin, a quo clan Catháin aka Ó Catháin of Cenel Ianna.
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Eoghain Ua Catháin, Abbot of Cluain-fearta-Brennain (Clonfert, Co Galway) died 980 AD (Ref: Annals of the Four Masters).
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unknown Ó Catháin chief, likely died at the battle of Clontarf in 1014 with other chiefs of Connacht.
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Gerald O Catháin, most learned man in the order of canons, died 1226. Ref: Annalexts Connachta.