This kinship chart is something I have been trying to determine for almost thirty years! As teenagers, my friends and I would watch Late Night with Conan O’Brien. We watched an episode on October 23, 1996 with guest Denis Leary, who told Conan that “my grandfather and your grandfather were first cousins.” Leary then goes on to say it goes through his O’Leary ancestors and so for Conan it must go through the Reardon family, with Conan acknowledging that Reardon is his mother’s maiden surname. The interview goes on discuss how the families had interactions with one another in Worcester, Massachusetts after Leary’s father and uncle had emigrated from Ireland in the 1950s. As they cut to a break, Leary pulls out a piece of paper from his jacket pocket to show him their family connections (with no way to zoom in on my recorded VHS!). Based on this interview, it has been widely reported that Leary and O’Brien are third cousins.
Having been interested in distant kinships between famous individuals through various colonial American ancestry (often from the thirteen American colonies or French Quebec), distant Irish derived kinships between two famous American individuals are considerably less common. This has to do with Irish immigrants coming from many parts of Ireland in the 19th century and arriving in many different cities in the United States. Thus, there is not the chance for these families to stay in the same area for several generations, with descendants then spreading out across the country.
Still, this kinship I learned when I was fifteen years old intrigued me. The next summer I worked at the New England Historic Genealogical Society (now American Ancestors), and I would take the commuter rail train to Boston from Worcester, where Denis Leary and Conan O’Brien’s parents were all born. I visited the Bureau of Vital Records in Boston a few times and attempted to figure out the exact kinship between Leary and O’Brien.
Based on the way Leary described the kinship, my initial guess was that Denis Leary’s paternal grandfather’s mother was a Reardon. While I was able to trace several generations of O’Brien’s ancestors back in Massachusetts (as his ancestors largely emigrated from Ireland to Massachusetts in the mid-19th century, making Conan either fourth or fifth generation American in each line), tracing the immediate ancestry of Leary was more difficult. His parents were the immigrants in the mid-20th century, and getting access to 20th century Irish records for myself in the 1990s was limited. I determined Conan’s maternal grandfather, James Francis Reardon (1896-1976), was the son of Patrick J. and Margaret (Marshall) Reardon (also spelled Riordan), both of whom were born in co. Kerry, and moved to Worcester where they were married in 1893.
It did not appear that either of Patrick or Margaret’s parents left Ireland, so I was trying to determine which of Patrick or Margaret’s sisters married a Leary (or O’Leary) and had a son John Leary, who was Denis’s paternal grandfather.
Two decades later, with more Irish records becoming available online, I was able to look at the siblings of Patrick and Margaret, and there was no sister that married a Leary. Further, I was able to extend the lineage of John Leary as well. John Leary was the son of Patrick O’Leary and Catherine Daly, who married in Kilcummin, co. Kerry, in 1878. With Patrick Reardon’s parents being Reardon and Marshall, I couldn’t figure out how he could be first cousins to a child of a Leary and a Daly. Oh well, I let this sit for another decade.
Most recently, the Leary O’Brien kinship was mentioned again when Leary appeared on O’Brien’s podcast “Conan O’Brien Needs a Friend,” and this time several colleagues sent me the link. So, I decided to take another look, and finally I figured it out! All I had to do was go one more Reardon generation back. Conan’s great-grandfather, Patrick J. Reardon (1866-1898), was the son of John and Margaret (Daly) Reardon. Margaret was the daughter of Eneas and Julia (Sheehan) Daly of co. Kerry, and their other daughter was Catherine Daly, wife of Patrick Leary! So, when Denis Leary said his grandfather and O’Brien’s grandfather were first cousins, he should have said they were first cousins once removed, i.e. Leary’s grandfather and O’Brien’s great-grandfather were first cousins, and as such Denis Leary and Conan O’Brien are third cousins once removed (see the chart below).
It feels really great to get this kinship resolved thirty years after learning it!
