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  • Writer's pictureColleen Murray

My Irish Y-DNA project: breaking through brick walls

Irish research can be difficult, due to record loss or how the records were kept in the first place. When records fail us, sometimes DNA can come to the rescue. This is a case study from my own family, based on my father’s Y-DNA results and how we used them to rule out a hypothesized relationship in his family tree.

I have permission to use my dad’s results for these post, but the first names of everyone have been changed for their privacy.

I tested my dad’s Y-DNA back in 2014. For the next 5 years, he did not have another match to anyone with his surname. He matched several men with the King surname, which is an anglicized version of our surname, Conroy, so I wasn’t concerned. Dad just didn’t have any close matches at all yet. Fast forward to 2019, when Dad finally got a Y-111 match to Richard Conroy!

Richard matched dad at a genetic distance of 4, meaning that on 111 markers, Richard and dad matched on 107 of them, and did not match on 4. Richard is from Australia, and we weren’t sure how we were related, but in general, your matches with a lower genetic distance will usually be the closest related to you.

Richard’s immigrant ancestor was named David, and he was born about 1819 in either Mitchelstown, County Cork, or maybe County Tipperary, depending which record you consult.[1] David was married in New Orleans in 1850, and then he and his wife emigrated to Australia and had several children.[2] David’s death registration reported that his parents were Michael Conroy & Catherine Burnett.[3]

My dad’s immigrant ancestor was also named David, but born about 1791, and he came from Ballydeloughy, County Cork which isn’t far from Mitchelstown. He immigrated to Ontario, Canada in 1825 as part of the Peter Robinson Immigration project. (See my blog post “Have you been looking in the wrong place?” for research and citations). He had a son named David, born about 1819 who emigrated along with the rest of the family, however, we had no further records on him in Canada, so we weren’t certain what had become of him.

Research Question: Could Richard’s ancestor David, be David jr., the missing son of my ancestor David Conroy and his wife, Catherine Sullivan? The ages and birth locations certainly aligned, and several online family trees already reported this relationship as if it was fact, although we could find no corroborating documentary evidence supporting the conclusion.

Here is a diagram of the hypothesized relationship between Dad & Richard:

Work on the Paper Trail

I worked with Richard’s sister, Rachel, the Australian family genealogist. She had attempted to find the New Orleans marriage for her ancestor, but had not been successful. Australian David’s death registration, as described above, did not support our hypothesized relationship- it named totally different parents, although the mother’s first name was consistent. Since the son who was the informant on David’s death would have never met his Irish grandparents, and these sorts of errors are common, I did not feel that the paper trail entirely ruled out the possibility of our hypothesized relationship. Since Australian David reported a marriage in America, we at least knew he had immigrated to North America prior to going to Australia, so although it would mean a lot of travel for a young man in this time frame, it was not outside the realm of possibility that he had gone from Ireland, to Ontario, to New Orleans and then settled in Australia.

The Irish paper trail is not likely to help us further in our quest. The parish records in Ballydeloughy begin after my Conroys left Ireland, and we did not find any David Conroys baptized circa 1819 near Mitchelstown or in Tipperary.[4] Most probate records burned down in the 1922 Public Records office fire, and Irish censuses aren’t extant prior to 1901.

But could DNA step in where the paper trail had gone cold?

My dad and Richard had both done the FamilyTreeDNA “Family Finder” autosomal test, in addition to their Y-DNA tests. But they were not autosomal matches. Rachel and I had both tested at AncestryDNA, but do not match. Rachel and Richard checked their other autosomal matches at and none appeared to descend from my David Conroy & his wife Catherine Sullivan. Some of their matches descended from other Cork Conroys, but dad and I do not match these people. I tested my dad at AncestryDNA, but still we did not get a match to Rachel, nor the other people with Cork Conroys in their tree who match Rachel.

My dad would be a 4th Cousin to Rachel and Richard if our hypothesized relationship was correct, and there is no guarantee that you will match autosomally with someone who is more distant than your 2nd cousin, so the lack of an autosomal match didn’t rule out our hypothesis, but it certainly didn’t support it either.

So what next?

I decided that we needed more information. We both agreed to upgrade the Y-DNA tests to the Big Y-700, and I recruited two more known descendants of my David Conroy & Catherine Sullivan to test. These new testers “Joe” and “Ben” were 4th cousin and 3C1R (third cousin once removed) respectively to my dad, and 2C1R to each other.

When you do the Big Y-700 test, you get both SNP and STR results. (I won’t get into the differences here, but both use mutations on the Y Chromosome to interpret how closely related you might be to someone). The Big Y-700 test comes with the Y DNA-111 STR results as well, as part of your package. The Y-111 results arrived a few weeks prior to our Big Y results.

Interestingly, when I looked at Dad’s matches to our mini-test group at the Y-111 marker level, Joe matched Dad at a genetic distance (GD) of 0 and Ben matched Dad at a GD of 3. This is interesting, because my dad is actually more closely related to Ben than he is to Joe. This is why using an STR test like the Y-111 test alone is not actually that great a predictor of how closely you are related to someone, due to the randomness of mutations, and the fact that markers can back-mutate.

But when we received our Big Y-700 results, our relationships were all clarified, and we learned that our hypothesis was wrong.

The Big Y block tree sorted Dad, Joe and Ben all onto the same branch of the tree, and right now our terminal haplogroup is R-B190586. Richard, on the other hand, was sorted into R-FTA77102. Ben, Joe and Dad share several SNPs in common, in the white box above their names. At first, I didn’t recognize the significance of this, but when I did, it broke through a huge brick wall.

Each SNP mutation happened in one man. Unlike STR mutations that might go forwards and backwards again, SNP mutations happen once. So since Dad, Joe and Ben are all positive for the SNP BY190506, for example, then they all got it from one of their mutual patrilineal ancestors. Whichever man first had the SNP mutation BY190506, he gave it to all his sons, who gave it to their sons. With this information, you can build a SNP family tree.

I realized that since Dad, Joe and Ben’s most recent common ancestor was David Conroy (b. 1791), then in order for all 3 men to share BY190506, then they must have got that SNP from David (b. 1791). That doesn’t mean it originated in David- it might have come from his father or grandfather etc. But David must have had it, in order to have passed it onto all 3 of these men.

If Richard was really a descendant of David (b. 1791), he would also have inherited BY190506, and all the other SNPs that Dad has in common with Joe and Ben, because David would have passed it onto all of his sons, who in turn would have passed it onto all of their sons. Since Richard doesn’t have these SNPs, he cannot be a descendant of David (b. 1791).

Yes, Dad, Richard, Joe and Ben share a common patrilineal ancestor, but it is someone further back than my David.


You may have heard that the Big Y test is only useful for research into your ancient line, not in a genealogical time frame. You may have heard it’s only worth upgrading to the Big Y if you have a good patrilineal tree going back 8 generations. You may have heard that the Big Y is only for experts. None of this is true anymore, and people are using their Big Y results to break through brick walls every day.

What is true, is that the Big Y is most valuable when you create a test group of other known family members and compare your group’s results to your unknown matches. So, you may need to recruit some more testers to get the most out of your own results.


Ideally, researchers are recommended to follow the “Rule of 3”, meaning you test one man, then one of his close male family members (like a son, brother, father, uncle, nephew, first cousin), and then a more distant man, like a 3rd-5th cousin. This should break up your private variants and confirm all your results. We are still working on getting closer to the Rule of 3 on our project. You can learn more about the Rule of 3 on the FTDNA-BiGY Facebook group, and this group is also an excellent resource on understanding your Big Y results.

In our Conroy mini-project, we need to get some more testers to break up, confirm and name the green private variants above both of our branches in the block tree. That way, in case, by chance there were any testing issues or no-calls, our conclusion will be confirmed via additional testers. So if you are a Conroy male potentially on this line, we encourage you to take the Big Y-700 test from FamilyTreeDNA to help us learn more about our shared family tree! The tests go on sale usually a few times a year, often around father’s day.

[1] Australian birth registration, Lamplough, Victoria, James Conroy (1860), no. 7 and Great West, Victoria, William Conroy (1868), no. 177. [2] Ibid. [3] Australian death registration, Great Western, Victoria, David Conroy (1886), no. 9323. [4] “Parish baptisms in Birth, Marriage, Death & Parish Records,” database, FindMyPast ( : accessed 13 March 2022), search for David Conr*y born about 1819 in Counties Cork or Tipperary; citing “Catholic Parish Registers,” images, The National Library of Ireland (, Dublin.

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