We are a dedicated group of people interested in the heritage of those family groups who historically descend from Conn Cétchathach, AKA Conn of the Hundred Battles. From the Irish annals, he was a High King of Ireland who lived ~125 AD. From him descend many of the important medieval dynasties of the northern half of Ireland, which was known as the Leath Cuinn, or the Half of Conn. We use modern surnames, Irish genealogies, and Y-DNA sequencing results to attempt to fit what the science of genetics reveals into the heritage of the historical Dál Cuinn, or 3 Connachta and the Ui Niall. Two of the most well known Dál Cuinn dynastic groups are the Teóra Connachta and the Uí Néill. The Teóra Connachta were composed of the Uí Briúin, the Uí Fiachrach, and the Uí Ailello; this last dynasty either dying out or being exterminated in the first millennium AD. All four of these dynasties were originated by one of the sons of Eochád Muigmedón, who was descended from Conn Cétchathach and also a High King of Ireland ~350 AD. The Uí Briúin descend from Brión, the Uí Fiachrach from Fiachra, and the Uí Ailella from Ailill. These three men were full brothers from Eochád Muigmedón’s first wife Mongfind. The Uí Néill descend from Niall Noígíallach, or Niall of the Nine Hostages. He was the paternal half-brother of Brión, Fiachróe, and Ailill from Eochád Muigmedón’s second wife Cairenn Chasdub. The Y-DNA results that we have seen so far indicate that the R1b-DF104 phylogenetic node is the starting clade (Y-Haplogroup) of the Dál Cuinn. The median age estimate for R1b-DF104 places it ~36 AD. This is a little before Conn’s time frame, so there may be subclades of R1b-DF104 that are not Dál Cuinn; but R1b-DF104 is the closest major clade with an origin near to the time frame of Conn, so it was decided to be overly inclusive rather than overly exclusive. The conclusion to associate the R1b-DF104 clade with the Dál Cuinn is based on the numerous Connachta surnames in the publicly available R1b-DF104+ test results that genetically correlate very well with the historical Irish genealogies and annals for the most part. As of August 2022 AD, there are over 2050 known R1b-DF104+ men. However, some egregious discrepancies have been discovered. Some of the more crucial discrepancies are listed below: The Dál Cuinn are not descendants of Éremón; that is, our Y-DNA does not seem to match up with the other dynasties who claimed Éremón as an ancestor. The Cland Colla/Airgíalla are not Dál Cuinn. Please see the Y-Haplotree chart for the Dál Cuinn. Also please visit Peter Biggins’s excellent website for a detailed explanation of the Cland Colla Y-DNA. The Uí Maini are not a single dynastic group, but appear to be a possible confederation of several dynastic groups. The Uí Briúin Aí descend from an earlier branch than the Uí Briúin Seóla and the Uí Briúin Bréifne. A member of the O’Conor Don family graciously consented to having his Y-DNA sequenced and his results fell exactly where anticipated among the Uí Briúin Aí families. But the traditional genealogy of the three brothers Dau Tengae Umae (Uí Briúin Seóla), Fergnóe (Uí Briúin Bréifne), and Eóchád Tírmchárnae (Uí Briúin Aí) is not possible genetically. While the Uí Briúin Seóla and the Uí Briúin Bréifne do descend from a common paternal ancestor, the Uí Briúin Aí had already split off before this ancestor.