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Are you stuck at your great-grandmother? Was your grandfather a foundling? Did your mother grow up not knowing who her father was? These are cases where DNA could help you break through that particular Brick Wall and reveal a wealth of information about your family tree that you could never have dreamed of.

Using DNA Results in Irish Genealogy

Some of the most important questions that we as human beings ask ourselves are: who am I? and where did I come from? It is the reason why many of us start researching our family tree and attempt to find the connection to our ancestors and the places where they lived. These questions are even more pressing for people who don’t even know who their immediate ancestors are.

For many years now, DNA has been helping Irish adoptees, and those with unknown fathers, to identify their biological parents, thus connecting them with a hitherto unknown family history, which in turn engenders a deeper sense of belonging and identity. But the techniques used with adoptees can also be applied to people who are searching for an unknown grandparent or great grandparent.

This article describes the steps involved in trying to identify the unknown parent of someone in your family. It could be you, it could be your father, it could be your grandmother. It could be anyone.

Let’s start off by using you as an example. Let’s assume that you don’t know who your biological father was. Here’s is what you do to find out.

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Get your DNA on the commercial DNA databases

Firstly, do the DNA test with Ancestry and once you have your results, you can download a copy of your DNA datafile to your computer and then upload it to several other databases for free, namely:

There is one other major company you could consider testing with (23andMe) but only if you don't solve the mystery with the close matches you get in the other databases above.

Will you find close genetic matches? Yes!

If you are very lucky, your DNA results will include a very close match (e.g. sibling, aunt, nephew) and you will be reconnected with your paternal biological family in a matter of days or weeks. 

Most people don’t have such very close matches, but they are occuring more frequently as more people join the DNA databases. A 2021 survey found that very close matches occur in about 15-20% of Irish & British test-takers. It’s more likely that your closest match will be a second cousin, or if you’re fortunate, a first cousin. Both of these scenarios are good news and it could be relatively easy to solve your mystery. 

What then follows is a sequence of steps to figure out who is the common ancestor you share with your close match (or rather, who is the common ancestral couple – because most of the time you will share an ancestral husband and wife in common).

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Success Rates in Irish & British cases (2021) vs US cases (2016) of unknown parentage
from Journal of Genealogy & Family History

Some people do this work on their own (because they want to, and have a good grasp of the technical aspects of the process). For those who need help, there are professional genetic genealogists who can provide assistance (some charge a fee), or there are volunteer genetic genealogists who can help free of charge - if you are interested in this option, check out the following groups on Facebook: DNA DetectivesSearch Squad.

Five Steps to Solving you Mystery

Here are the technical steps in the process.  Often, these steps are done in parallel rather than in sequence. And always we are looking out for a shortcut that allows us to jump ahead. It’s like a game of Snakes and Ladders – sometimes we get a match that allows us to skip a few steps ahead, and other times we are sent right back to where we started!

1. Check for a Quick Win

Is there a very close match at the top of your match list? Anything >700cM suggests a 1st cousin or closer. And if they have a good family tree available, you may be able to figure out who your parent is fairly quickly. 

And if that is the case, they will be able to see you too and the cat may be out of the bag very quickly. But if you are not ready to tell your story, you may wish to turn everything off i.e. privatise your account so that no one can see you as a match. Making yourself unseen and incognito allows you to create some breathing space for yourself, and give yourself some time to think about what you want to do next. 

You may want to see if you can find any of these new family members on Facebook just to see what kind of people they are. You may even find some photos of your parent or half-siblings. And then, when you are ready, you can attempt to make contact.

2. Cluster your matches into distinct genetic groups

Matches who match each other probably all share the same common ancestor. The goal here is to try to get at least four groups of "matches who match each other". Hopefully two of these four groups will be on your paternal side (one connected to you via your father's father and the other via your father's mother) and two will be on your maternal side (one via your mother's father, the other via your mother's mother).

I usually start with the first match below 200cM. On Ancestry, this involves selecting this first match, clicking on Shared Matches, and putting a coloured dot beside this first match and each match who matches you both. This creates the first genetic group. 

Then return to the main match list and repeat the process with the next match <200cM who doesn't have a coloured dot beside them. This creates the second genetic group. And then repeat the process for the third and fourth genetic groups. You will find that your closest matches will probably have several coloured dots beside them i.e. they belong to two or more groups. You can try to repeat this process with the other websites (MyHeritage, FTDNA, etc) but you may find that the genetic clusters are much smaller.

In this working example, we are looking for your biological father, so the matches on your mother’s side of the family are not relevant to that search. Ancestry now have a handy feature that automatically separates your matches into Parent 1 and Parent 2, but does not tell you which parent is which. However, you might easily figure this out for yourself if you recognise any known maternal cousins among the list of your matches – any matches you share with that known cousin will be related to you via your mother’s side of the family, and these can be put to one side and ignored. The remainder will be on your biological father’s side. 

If you don’t recognise any maternal cousins on your list, you could ask a known maternal cousin to test. Any matches you share with that cousin are maternal – the rest are paternal, and those are the ones you want to focus on.

3. Identify the common ancestors for each cluster

You can organise and analyse your clusters in any way you want. You can simply use a pen and paper. I prefer to use a spreadsheet and you will find an example of this Cluster Analysis Spreadsheet in a previous IXO article here.

On Ancestry, starting with the cluster with your closest matches, compare the family trees of everyone in the cluster and see if you can identify a common ancestral couple (or at least a common surname or ancestral location). I usually open each tree in a new tab (in pedigree view) so that I can rapidly go from one to the next and do a quick scan of the most distant ancestral surnames looking for surnames that repeat in several trees.

Sometimes a family tree is not available because your match has not shared it publicly online, so you will have to ask them nicely for it. And that means engaging them in a conversation initially and developing rapport and a trusting relationship with them over time. And this could take weeks or months because some people do not check their messages. I will usually send a brief but friendly initial message as a "way in" (see below) followed by several "nudge messages" over the subsequent months (e.g. "Hi Joe, just wondering if you have had a chance to read our previous message?"). 

Hi Joe

We seem to be quite a close DNA match.

Do you have any ancestors called Burton or Taylor?

Or any ancestors from Cork?

Looking forward to figuring out the connection.

Warm regards, Maurice

Example of a brief, friendly initial message

Once you have identified the likely common ancestral couple, try and figure out at what level you are likely to sit within their tree. You can do this by assessing the amount of DNA you share with each member of the cluster. The Shared cM Tool can help you figure out your relationship with each match. It also has a handy Relationship Chart with the average amount and range of DNA shared for a wide variety of relationships from half-sibling to 7th cousin. Just enter the amount of DNA you share with a person and the Shared cM Tool will generate a list of possible relationships with probabilities for each one. You can probably rule out some of the possibilities based on the age of your match (if you can find it or figure it out) - for example, if you are 40 and they are about 75, then they are likely to be your parent's generation and thus would be a "once removed" cousin to you. For difficult-to-place cases, I use the WATO tool to generate the most likely scenario.

Be aware that the Shared cM Tool does not take into account double-connections e.g if you are related to a match via TWO ancestral lines (e.g. you are related to them via both your father AND your mother). These double (or more) connections are quite common in small isolated rural communities ... and there are lots of them in Cork, Kerry & Donegal. That's how I lost my hair.

I put everything into a private, unsearchable family tree on Ancestry (you don't need a subscription for this). In that way you can maintain your privacy and you don't have to worry about other people being able to see what you are doing. You can also be as experimental as you like without having to worry about other people copying any mistakes into their family trees. Copy across potential relatives and ancestors from the trees of your matches and any other trees you find on Ancestry (or elsewhere). There are lots of tutorials online about how to build these "mirror trees" (google them).

4. Trace trees forward in time to identify candidates for your biological parent

Having identified the “most likely” common ancestral couple, trace all their descendants down to the present day (using other people's family trees, available records, and asking your matches). If your estimations are correct, one of these descendants will be your biological father … but which one?

There are several tricks you can use to identify the most likely candidate for your biological parent:

  • If you already know the identity of your biological mother, then you know you are looking for your biological father and therefore you only need to identify family lines that have males of the right age to be your parent
  • Look at locations. If you know where your conception is likely to have occurred, then there may be only one person from the list of descendants who was in “the right place at the right time” 
  • Your ethnic makeup may give clues to the likely person (e.g. his or her mother may have been from a distinctive ethnic group, and this may be reflected in your ethnic makeup results) 
  • There may also be clues from your Y-DNA or mitochondrial DNA results, and from the amount of X-DNA shared (which requires understanding the technicalities of DNA transmission) 
  • Identify your grandparents. If there are several candidates for (say) your grandfather, research their wives' family trees and see if they connect with a surname in one of the other clusters that you identified initially. 

5. Approach potential candidates for information (and DNA)

Armed with your theory, supported by the evidence, you decide to approach your potential close biological family (maybe a potential half-sibling). This is when the emotional rollercoaster really takes off. You can imagine how delicate this last step can be. You may benefit greatly from using an intermediary, particularly someone with professional training in reconnecting adoptees with their birth families. You usually only get one shot at this. 

If you have a social worker, you may wish them to make contact on your behalf ...  or use some other form of intermediary. It is often very helpful to have someone act as a buffer between you and your biological family. Or you may wish to contact them yourself (e.g. via the Ancestry messaging system, or via Facebook messenger, or simply sending them a letter). There is no right way to do this and you have a choice of various options, each with their pros and cons. Trust your gut feel when you get to this stage.

Initially you do not ask them to do a DNA test. You introduce yourself, tell them your story, and ask them if it rings a bell - is there a story within the family of a child being given up for adoption? You could consider mentioning the surname of your known biological mother and ask if anyone was romantically involved with someone by that name? And you could also discuss the DNA evidence that led you to their door. If you are lucky, one of the family might suggest: "would it help if I did a DNA test?" ... in which case you could say: yes, that would be great if you could. And their results may be the final piece of the jigsaw puzzle that you need to identify your biological father.

Applying the Process to Generations further back

So, the above is an example of how to solve an unknown parentage case as if you were the subject concerned. But what do you do if the person involved was your deceased parent or grandparent? Well, it’s exactly the same approach but with a specific adaptation.

You can still use your own DNA, but you will need to identify and isolate those DNA matches that relate to the person of interest. So for example, if your mother did not know who her father’s parents were (i.e. your great grandparents), you would need to 1) identify which of your matches are on your mother’s side, and then 2) which of those matches are only on your mother’s father’s side.

To do this, first you could test someone on your father’s side of the family (test your father if he is still alive, or his sister, or a paternal 1st cousin, etc). Any matches that you share with that paternal relative will be on the paternal side of your family and all of these matches can be put to one side and ignored. What you are left with are those matches that are likely to be only on your mother’s side of the family. Alternatively you could test a maternal 1st cousin, and this too would help identify which of your matches are on your maternal side.

Secondly, you could test a relative on your mother’s mother’s side of the family (e.g. your maternal 2nd cousin) as that would help you identify which of your matches are related on your mother’s mother’s side (which you could then ignore), thus isolating the matches that are related to you via your mother’s father.

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You then apply the 5 steps above to this subset of your matches and with a bit of luck you will be able to figure out who your mother’s father was.

You should always ask yourself the question: is there anyone else within the family that I could test whose DNA would add more information to what I already have? Or whose results could help me narrow things down further? As a general rule of thumb, test the older generation if they are available (and willing) – they will have twice as much relevant DNA as the next generation down.

About 3-4 million people join the DNA databases every year so as time goes by, the chances of solving your unknown parentage mystery get better and better. The first step is for you to do the test … and then convince a few targeted relatives to do the same.

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