Pater Familias O'Dea

The Family Tree of the early O'Dea families who lived in the Miltown area beginning circa mid-eighteenth century
     Combining the results of DNA testing with genealogical records (birth, marriage and Death) and other records (Tithes Applotment Survey, Griffiths Valuation records and Land and Tenure Books), we can postulate a Family Tree for the O’Dea Families from Aglishcormick that 1) is internally consistent and 2) extends the Family Tree farther back in history than paper records alone allow.

The oldest member of the tree, the Pater Familias of the O'Dea families in Limerick, was born circa 1714, probably in County Clare. From him, two distinct lines can be traced and either he or his descendants emigrated from Clare sometime between 1735 and 1755.

There were certain local disasters that might have led to this emigration including a remarkable span of weather that produced a year-round winter and froze the waters of the Shannon several feet thick at Limerick. This castastrophe brought on a massive famine, not unlike the one in the mid-nineteenth century, and it may have been the reason that so many families left County Clare circa 1740.

We postulate that this man, whatever his name may have been, had two sons: we will call the first "Line One" (John the Elder) who we postulate was born circa 1735 and the second "Line Two" (Thomas the Elder) who we postulate was born circa 1741. Line One has two distinct lines issuing from it and we identify these with historical persons (John born circa 1759 and Darby born circa 1756). Line Two has one distinct line issuing from it and we also identify it with an historical person (Michael, born circa 1771).


DNA tests show that three distinct, but closely related, lines issue from this "Pater Familias" and are represented by Edmond O'Dea of Ireland, Patrick O'Dea of Ireland and Dennis Day of the United States.

The relevant DNA clusters that distinguish these three lines are: DYS607 = 15, DYS464 = 13-13-13-17 and CDY = 35-37. We will note the relevant changes in these clusters in the following records beginning with the two lines we have postulated issuing from the Pater Familias.

  • There is a split between Dennis' and Edmond's line at the DYS607 marker. The mutation of the DYS607 marker to a value of 16 occurs only in Dennis' line and could have occurred anywhere in Dennis' line in generations 1 through 6. This marker distinguished between Edmond's branch and Dennis's branch of the Family Tree.

  • The mutation in the CDY marker occurs only in Patrick's line and could have occurred anywhere in generations 1 through 6 and distinguishes his line from both Edmund's and Dennis'.

  • There is a split between Dennis' and Edmond's line on the one hand and Patrick's line on the other at the DYS464 marker. The mutation of this marker from 13-13-15-17 to 13-13-13-13-15-17 distinguishes between Patrick's branch on the one hand and Dennis' and Edmond's on the other in the family tree.

In comparing Y-DNA 111 marker results, the probability that Edmuind, Patrick and Dennis shared a common ancestor within the last seven generation is 97.7%, within the last nine generations, 99.38%.

Line One linked below will lead to Edmond O'Dea and Dennis Day, and Line Two will lead to Patrick O'Dea.

Children of Pater Familias O'Dea

ChartsPater Familias O'Dea Descendant Chart (Indented)
Last Edited8 Feb 2021