This is an unusual group, with complicated relationships: There are 5 tested people, related in different ways. And they represent three entirely separate male-line Coffey families. (And I had to draw this picture in a rather tortured way, to make things fit togetherJ )





The first three members (Denis, David and Phillip) have y-DNA matches. For comparison purposes I’ve called Phillip the “reference”, and David matches him perfectly at the 37-marker test level. Denis seems more distant, and matches Phillip 64/67, and matches David 35/37. These are still excellent matches, and they are all three absolutely “cousins”.


The second two also seem closer to each other geographically. Phillip descends from an immigrant from Tipperary, and David is an Irishman now living in Dublin, but with roots in Kilkenny. These two counties are adjacent to each other. Denis thinks his line comes from Killarney, which is significantly farther to the north.


All three of these men have also done autosomal DNA (atDNA) testing, which has a relatively short range. Phillip and David do have an atDNA match, which suggests they are probably related within plus or minus one generation, as indicated by the uncolored box above. Denis’ atDNA test does NOT match, which rules out any really close connection. But using FTDNA’s Time Predictor (FTDNATiP) on the y-DNA result suggests there is maybe a 50/50 chance the connection is within the next few generations. Thus the dotted line with question marks.


The fourth tested person, Patrick, is connected to Phillip as above, but with a female in the line (Agnes). Phillip and Patrick thus both descend from Michael (1813), who is also from Tipperary. Patrick has an atDNA test, confirming their relationship. However Patrick’s y-DNA is VERY different, proving he is from an entirely SEPARATE Coffey male line. So Agnes did NOT marry a cousin!


The fifth person, Don, descends from a relatively recent immigrant from Kilkenny, and he is also on an entirely separate male line. However an autosomal DNA test says he is approximately a “fifth cousin” of Patrick.


The connections between the five lines are confirmed via both y-DNA and autosomal DNA testing, subject to the uncertainty of the “Unknown” boxes shown in white. See more discussion below.



We have autosomal test results on David and Phillip, and that test shows they are related within the range of second cousin to fourth cousin (2C to 4C). This is close enough that they can begin to talk about actually trying to figure out their MRCA (Most Recent Common Ancestor):


If Gilbert (1853 Dublin) and Thomas (1848 Tipperary) were brothers, then David and Phillip would be 2C1R. If Gilbert and Thomas were first cousins, then David and Phillip would be 3C1R. From a DNA perspective, both are between 2C and 4C, and thus consistent with the autosomal test.


However David says while Patrick (1822 Kilkenny) DID have a son named Thomas, that son is definitely NOT Thomas (1848). Therefore he favors the “Gilbert and Thomas were First Cousins” theory, and has been trying to investigate.


PATRICK, THE FOURTH PERSON: Patrick does NOT have a y-DNA match to Phillip. This proves that Phillip’s male-line ancestor Thomas (1848) is NOT from the same Coffey family as Patrick’s male-line ancestor Michael (1813). Even though Thomas and Michael come from the same general location, their non-relationship is not surprising. There are quite a few totally unrelated Coffey’s (at least not related through a male line) in the same general area.


We are convinced that Patrick and Phillip ARE related as shown above, that BOTH descend from Michael (1813). Phillip’s descent includes a female (Agnes) and therefore the y-DNA test cannot reveal that relationship. However the atDNA test indicates they are in the range of “second to third cousins”. That is absolutely perfect, because their actual relationship is 2C1R (second cousin once removed), which is exactly half way between a 2C and a 3C.



Don is well known to the “Coffey Cousins”. His family line comes from Kilkenny. The y-DNA test on his male Coffey line proves connection to the largest Coffey groups in America, those who descend from ancestors “Edward” and “Peter”. But when we arranged for Don to do the atDNA test, there was a complete SURPRISE, and the above Patrick came up as a “Fifth Cousin to Remote Cousin” match to Don! And Patrick and Don have entirely separate Coffey lines, per their y-DNA testing.


It is possible their autosomal ancestral connection is to some American family that the immigrant ancestors married after arrival in America. However that is less likely because Patrick’s line settled in Illinois, and Don’s line settled in New Jersey, and those are too far apart. It is much more likely that their connection is back in Ireland, given their roots in the adjacent counties of Tipperary and Kilkenny. Most likely, somewhere back there, their separate Coffey families married with a common non-Coffey family.


Without very detailed genealogical research within Ireland, it is doubtful their MRCA (most recent common ancestor) will ever be identified. But that ancestor is definitely back there somewhere!