9th century Connaught... The tribe of the Ui Briuin Breifne has migrated out of what is today central Roscommon, northward along the River Shannon into modern day counties Leitrim and Cavan. Within the Ui Briuin are two smaller fledgling septs, the Teallach Eachach ("Household of Eochaid") and Teallach Dunchadha ("Household of Dunchadha"). These two families' tribal areas through next millenium still have names derived from these septs: the baronies of Tullyhaw and Tullyhunco in County Cavan. The old gaelic genealogies name Eochaid and Dunchadha as both sons of Maenach, and grandsons of Brenainn. They are distant kin of the O'Rourkes and O'Reillys who are both descended of Brenainn's grandfather Feargna. Almost ten generations after settling, leading clans start to arise out of both of these families, mainly the MagSamhradhain (Magauran) who would be the chief family of Tullyhaw, and the MagThighernain (McKiernan) who would rule Tullyhunco, also called Clonballykiernan. Modern Y-chromosome research has proven the relationship of the Teallach Eachach and Teallach Dunchadha, and it is likely that the A5902 mutation could have occurred with Brenainn or a close descendant. We know it was not an ancestor of Brenainn because the O'Rourke and O'Reilly do not possess A5902. It's very likely that both Brenainn and Maenach had upwards of ten sons, aside from their two noted descendants, Eochaid and Dunchadha and there lies the mystery of who most of these A5902+ families are. These kindreds, mostly have no surviving written genealogies but were kin to these septs and settled somewhere in these areas or bordering regions nonetheless. The people who possess this mutation, although largely in Tullyhaw and Tullyhunco, also heavily populate the baronies of Loughtee Upper & Lower, Carrigallen in County Leitrim and Longford in County Longford. It is the goal of this DNA group to discover the relationships of the many branches of the A5902+ paternal lines, who may now be unofficially called the Cenel Brenainn. Their migrations throughout the rest of Ireland combined with the fluidity of surnames in the medieval period are already an obstacle, But their absorption of Scottish mercenary families who were billeted and living among them, the the loss of not only written records but entire bloodlines through the turbulent 17th century and subsequent famines, will prove this very difficult.