Recently a reader, Ian, dropped me a note suggesting that perhaps not everyone understands the 2-fer value of close family members who DNA test.
That’s “two for the price of one.”
Even just one family member like an aunt or uncle, or a great-aunt or great-uncle is a goldmine.
Here’s why.
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In the chart above, you, in green, obtained 50% of your DNA from each parent. Each of your parents gave you have of thier autosomal DNA.
Your parent shares approximately 50% of their DNA with their full sibling who is your aunt (or uncle,) shown in yellow.
Full siblings each receive half of their parents’ DNA, just not the same exact half. That’s why you need to test your own siblings if your parents aren’t BOTH available for testing.
You share about 25% of your DNA with any aunt or uncle, shown in yellow. Your 25% shared DNA came from your grandparents.
The Important Part
But here’s the really important part:
- ALL of the DNA that your aunt or uncle carries is your ancestors’ DNA too – even though you only match your aunt/uncle on 25% of their DNA.
- ALL OF THEIR DNA IS AS RELEVANT TO YOU AS YOUR OWN!
- The other 75% of the DNA that they have, and you don’t, was inherited from your grandparents. There’s no place else for your full aunt or uncle to receive DNA.
You can utilize the DNA of a full aunt or uncle JUST LIKE YOU UTILIZE YOUR OWN MATCHES.
The 2-Fer
Here’s the 2-fer.
- Anyone you match in common with your aunt or uncle is identified to those grandparents or their ancestors. That’s about 25%.
- Anyone that your aunt or uncle matches in common with another family member that you don’t match but where you can identify the common ancestor provides you with information you can’t discover from your own DNA.
Their Matches are “Your Matches” Too – ALL OF THEM
Yes, all of them – even the people you don’t match yourself – because ALL of your aunts or uncles ancestors are your ancestors too.
Think about it this way, if you and your aunt both have 4000 matches (as an example) and you share 25% of those – you’ll be able to assign 1000 people to that parent’s side of your tree through common matches with your aunt.
However, your aunt will have another 3000 matches that you don’t share with her. All 3000 of those matches are equally as relevant to you as your own matches.
This is true even if your parent has tested, because your aunt or uncle inherited DNA from your grandparents that your parent didn’t inherit.
So instead of identifying just 1000 of your matches in common, you get the bonus of an additional 3000 of your aunt’s matches that you don’t have, so 4000 total matches of your own plus all 4000 of hers – 3000 of which are different from yours! That’s a total of 7000 unique matches for you to work with, not just your own 4000!
| Your Matches | 4000 |
| Aunt’s Matches | 4000 |
| Common Matches | -1000 |
| Total Unique Matches | 7000 |
Moving Back Another Generation
If you’re lucky enough to have a great-aunt or great-uncle, shown in peach, the same situation applies.
You’ll share about 12.5% of your DNA with them, so you’ll only share about 500 of your 4000 matches, BUT, all 4000 of their matches are in essence your matches too because your great-aunt or great-uncle carries only the DNA of your great-grandparents, giving you 7500 unique matches to work with, using our example numbers.
Every aunt or uncle (or great-aunt or great-uncle) will provide you with some matches that other family members don’t have.
Whatever analysis techniques you use for your own DNA – do exactly the same for them – and test them at or transfer their DNA file to every vendor (with their permission of course) – while you can. Here’s an article about DNA testing and transfer strategies to help you understand available options.
Genetic Gold
Their DNA is every bit as valuable as your own – and probably more so because it represents part of your grandparents and/or great-grandparents DNA that your own parents and/or grandparents didn’t inherit. Without aunts and uncles, that DNA may be lost to you forever.
If your parents or grandparents have multiple living siblings – test all of them. If they have half-siblings, test them too, although only part of half siblings’ matches will be relevant to you, so you can’t treat them exactly the same as full sibling matches.
While you’re testing, be sure to test their Y and mitochondrial DNA lines at Family Tree DNA, the only company to offer this type of testing, if their Y and mitochondrial DNA is different than your own. If you don’t understand about the different kinds of DNA that can be tested, why you’d want to and inheritance paths, here’s a short article that explains.
You can always test yourself, but once other people have passed away, valuable, irreplaceable genetic information goes with them.
Any DNA information that you can recover from earlier generations is genetic gold.
Who do you have to test?
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