Colmán Már (‘the great’) (d. 555/63), putatively a son of Diarmait and king of Uisnech, is accepted in some sources as eponymous ancestor of Clann Cholmáin, a dynasty of the Uí Néill. His father is identified as Diarmait (qv) (d. 565) son of Cerball, and his mother as Eithne daughter of Brénainn Dall. On that account, he appears as a half-brother of Áed Sláine (qv) and Colmán Bec (qv), and is assigned a sister (or half-sister) Lann, allegedly the wife of Duí Irlúachra of the Éoganachta. It can, however, be inferred that the brothers Colmán represent a case of duplicated identity. Aside from the coincidence of personal name, according to the ‘Banshenchas’ (lore of women), both had mothers who belonged to a ruling lineage of the Conmaicne. Besides, the floruit accorded to Colmán Már (he supposedly predeceased his father in 555, 558, or 563) poses certain difficulties; it implies that he was born probably in the 520s and named with an Irish diminutive formed from the Latin religious cognomen Columba, which is difficult to reconcile with the fact that Colum Cille (qv), probably a cousin of his father Diarmait, was born in 521 and may have taken that name only on entering the church. His early death also fits uncomfortably with claims that he was the father of Suibne, Fergus, and Óengus, who come to prominence only from the end of the sixth century.
A further consideration in relation to Colmán Már, whose inclusion in the regnal list of Uisnech is almost certainly anachronistic, is that – in marked contrast to his half-brother Colmán Bec – nothing is known of his career besides the alleged circumstances of his death. He is said to have been slain by one Dubsloit of the Dál nAraide, which in itself is not an unlikely end for an Uí Néill dynast at this time: the ruling lineages of Ulster still extended sway as far south as the Boyne and seemingly contested the kingship of Tara with the dynasty of Diarmait. The latter, indeed, appears to have been slain by Dál nAraide opponents. It is clear that a group of powerful early-seventh-century Uí Néill dynasts, who supported the emergence of Uí Dúnlainge in Leinster, were sons and grandsons of one Colmán. However, the emergence of the lineage which became known as Clann Cholmáin, most likely associated with Murchad Midi (qv) and his brothers in the late seventh century, ultimately led to a power-shift within Mide. With the parallel line of Follaman (d. 766) displaced and political power monopolised by the line of Murchad, it appears that genealogical recasting took place, which led to the creation of two personae for the eponymous Colmán.