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Tackling Irish Brick‑Walls with DNA – Which Company to Test With?

2025-10-11
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This piece was kindly submitted by Dr. Maurice Gleeson, founder of Genetic Genealogy Ireland and expert in practical guidance on how to use DNA to advance your genealogy.

Genealogy Tips · IrelandXO

When researching your family tree, most genealogists eventually reach a brick wall: an ancestor whose parents can’t be identified in existing records. No matter how many censuses, birth certificates, wills, or parish registers you search, the trail ends. DNA offers a new route through that wall.

It does this by identifying people with whom you share the same segments of DNA. And the reason why you share these same segments is because they were passed down to you and your DNA matches by the same ancestor. And if you compare your family trees, you will be able to identify who that ancestor was (in many cases). And your DNA matches may have information about that ancestor that you don’t … and discovering that information could lead you to the breakthrough you are hoping for, allowing you to identify the missing parents of your most distant known ancestor.

But not all DNA testing services are equally helpful in that mission. Below is a comparison of the major companies (Ancestry, MyHeritage, FTDNA, 23andMe, LivingDNA). The Rule of Thumb for Irish genealogy is: 1) test at Ancestry, and then 2) upload to other websites for free (see here). This is the most cost-efficient approach.

Also, DNA may put you in touch with fellow researchers who have been researching much longer than you have and they may have all the answers you need. This could be a wonderful shortcut to building your family tree back in time, further back than you could ever have imagined.

Why Ancestry Should Be Your First Choice

Massive match pool

Ancestry’s database is now over 27 million people strong (2025), making it the largest among the consumer DNA companies (see here). Having such a large datapool increases your odds of finding the right cousins to help you break through your brick wall.

Strong presence for Irish ancestry

If your ancestors come from Ireland, Ancestry is especially valuable. Many genealogists find their closest Irish matches are on Ancestry, simply because so many people with Irish roots have tested there.

Trees + records = actionable matches

A DNA match without an associated family tree is often useless (even if they’re a close relative) because you don’t know how they fit into your family tree. One of Ancestry’s strengths is that it has the most user trees and the largest integrated record collections (censuses, civil registers, etc.).

The best for identifying Irish “Ancestral Regions”

As well as giving you an “ethnicity estimate” (which tells you what percentage of your DNA comes from the different regions of the world), Ancestry is able to identify what I call “genetic hotspots’”in Ireland i.e. specific regions or counties from which your DNA may have originated. This can be very useful if you do not know where in Ireland your ancestor came from, and provides a useful clue as to which records you should focus your attention on.

Clustering allows you to group matches together

To help you see which matches are likely connected to the same ancestor, Ancestry introduced automatic clustering in 2025. Other websites (e.g. GEDmatch & MyHeritage) had done this previously, based on the elegant methodology developed by EJ Blom on his Genetic Affairs website (see here). Clustering can also be done manually by using the coloured dots system. The clustering process allows you to identify groups of Shared Matches who likely share the same common ancestor. This can be hugely useful if you want to focus your research on a particular ancestor of interest.

Separating your Parents (Parent 1 / Parent 2)

Ancestry is able to use their technology to divide most of your matches into two groups, which they call Parent 1 and Parent 2. By looking at your matches, you should recognize some close matches that are definitely on one side of your family tree or the other, and this tells you which of the two groups is on your father’s side and conversely which must be on your mother’s side (or vice versa). You can then relabel the relevant groups Paternal and Maternal. This division allows you to sort your matches into your maternal vs paternal lines without testing your parents.

Pricing Structure

AncestryDNA regularly goes on sale, but the standard test usually costs around £79–£99 in the UK, $99 in the US, or €99 in Europe (before discounts). That price gives you your ethnicity estimate and access to your list of DNA matches. However, some of Ancestry’s most powerful features are available only with a subscription or as part of the AncestryDNA Plus / Pro Tools packages. For example, a standard subscription unlocks Ancestry’s vast historical records and public family trees, which are often essential for working out how your DNA matches connect. Pro Tools add further DNA-specific features, such as chromosome painter views, segment detail, and enhanced clustering that help you group matches by ancestral line. In practice, you can begin with the basic test, but most researchers find that paying for access to trees, records, and advanced DNA tools significantly improves their chances of making a breakthrough.

To optimize cost-efficiency, you could start with the basic subscription for a few months, add in ProTools for a month or two, become familiar with how the website works, and then turn off all your subscriptions until you have enough time on your hands to devote a few hours each day to your genealogy. You will not lose anything if you cancel your subscription. Your tree and your DNA will still be there and full access can be “reactivated” at any time.

MyHeritage: A Close Second for Irish Research

In my experience, MyHeritage is the next-best site (after Ancestry) for finding matches with Irish ancestry. Its user base of almost 10 million includes many people with roots in continental Europe and the British Isles. It also allows clustering (either automatically, or manually using their coloured squares feature) and this can be very helpful for dividing your matches into distinct groups who descend from a specific ancestor.

Unlike Ancestry, MyHeritage offers some additional tools, including a chromosome browser and triangulation tools, enabling you to see which matches share overlapping segments of DNA and thus are likely descended from the same ancestor.

However, a key caveat: unlike in the past, you can no longer (as of recent security changes) upload a copy of your Ancestry DNA datafile directly into MyHeritage to gain matching. That may return in time, but for now you’ll often need to test directly at MyHeritage or rely on matches from people who also tested there.

FamilyTreeDNA (FTDNA) Essential tests for Irish Surname Research

Both Ancestry and MyHeritage use the autosomal DNA test. This test assesses the DNA from 22 of your 23 pairs of chromosomes. The last pair (Pair 23) is also known as the sex chromosomes (X and Y). Women have two X chromosomes; men have an X and a Y chromosome. The X chromosome is usually tested as part of the autosomal DNA test, but the Y chromosome has to be tested separately, and only FTDNA provide Y-DNA tests that are good enough for researching a specific surname.

Irish surnames are classed as fixed inherited patronymic surnames. In other words, they arose about 1000 years ago, were based on the name of a famous ancestor (e.g. O’Brien, meaning descendant of Brian), and were passed down the direct-male-line from father to son, through the ages to the present day (they were also passed from fathers to daughters, but the daughters changed their names when they got married and did not pass it on to their children, and thus the direct connection to the surname was lost).

In a similar fashion to surnames, Y-DNA is passed from father to son (daughters do not get a Y chromosome), and thus, because Y-DNA and Irish surnames are passed hand-in-hand from father to son, Y-DNA is a useful marker for Irish surname research because it follows the direct-male-line back in time (father, father, father, etc) to the origin of Irish surnames (about 1000 years ago) and beyond that into the medieval Irish clan era (pre-1000 AD).

FTDNA have over 10,000 Y-DNA projects, most of them devoted to the research of specific surnames so if you have a surname you want to research, just google “FTDNA” and the surname, and you should be able to see if there is a Surname Project for that specific name. They are free to join, run by volunteer administrators, and can provide essential information about your surname of interest.

Start with the basic Y-DNA37 test ($119) and (based on advice from your project administrator) upgrade to the Big Y test ($300+) if need be. Wait for the sales for discounted prices.

FTDNA also does autosomal DNA analysis, and you can upload your Ancestry or MyHeritage DNA datafile for free (see here), but their autosomal database size is only about 2 million, so you are less likely to get relevant Irish matches. UNLESS … your ancestors came from the north of Ireland (any of the nine counties of Ulster). The North of Ireland Family History Society (see here) has created the largest autosomal DNA database of people who currently live in the north of Ireland, so if you have tested at Ancestry you MUST upload your data to FTDNA in order to access relevant matches who still live in the north of Ireland. AND you must join the NIFHS DNA Project on FTDNA (see here).

There are two further important points about FTDNA.

Firstly, they also offer the best mtDNA tests for genealogical research. mtDNA is short for mitochondrial DNA and it follows the direct-female-line (mother, mother, mother etc). It can be a useful test if your are specifically researching this particular ancestral line.

Secondly, all the autosomal DNA tests (from any company) have a reach of only about 250 years, so they may take you back to ancestors who lived in the 1750s or thereabouts, but beyond this timepoint it becomes increasingly difficult to interpret any results. So if your Brick Wall ancestor is before 1750, you need to think about using Y-DNA instead. And if you don’t carry the surname of your Brick Wall ancestor yourself, find a cousin / relative with the surname and get them to do the Y-DNA test (as your proxy). But beware – you are not going to find many Irish records prior to the late 1700s unless you are very lucky or your ancestors were landed gentry. In most cases, records simply do not exist, because they were never collected in the first place.

23andMe - Medical Risk Assessment

This company is more focused on assessing risk factors for a variety of medical conditions and many of the people in the database have no interest in genealogy. The database mainly contains people from the USA and relatively few from Ireland, but it has the second largest database (15 million) so could be worth exploring if you do not break through your Irish Brick Wall using the other companies.

LivingDNA - Useful for Ancestry from Britain

LivingDNA’s specialty is regional ancestry breakdowns across the UK. Its ancestry estimate is more precise for British ancestry, but less so for Irish ancestry. While its matching database is small (about 500,000), its regional detail can sometimes offer clues about county-level origin. But on its own, it’s unlikely to solve a brick wall - better as a complementary test. And you can upload your DNA datafile from any other company for free (see here).

Closing Thoughts

Analytical tools (chromosome browsers, clustering, triangulation, phasing) can be immensely helpful in organizing your research, but no tool replaces the power of human contact. Most of my breakthroughs have come from getting in touch with my matches and asking the right questions. One of your matches may have a record that you missed, or may have family lore that provides you with the information you need to go back to the records yourself and make that breakthrough. Occasionally matches have records that are not in any public repository (e.g. the family bible, the letters in the attic, notebooks from an ancestor) and these are the key to making a wonderful breakthrough. They key to success is talking to people.

So test at Ancestry, upload your data for free to the other websites, identify matches that are relevant to your Irish Brick Wall, contact your matches, ask the right questions … and if you throw enough mud at your Brick Wall, some of it is bound to stick.

Somebody somewhere out there knows something that you don’t.


Maurice Gleeson
Genetic Genealogist
Sep 2025
Website: DNA & Family Tree Research


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