How Can Siblings Have DNA Showing Different Ethnicity Estimates?

If you have a DNA test performed and it shows 35% German ancestry, 25% Irish ancestry, 10% Scandinavian ancestry, and the rest from the Middle East, does that mean your brother or sister will show exactly the same results if they also take a DNA test? Actually, the answer usually is “no.”

How can full-siblings have different ethnicities when they have the same parents? It’s a consequence of the complex relationship between genetics, ancestry, and ethnicity.

It is usually because one sibling received more or fewer genes from one parent than the other. In contrast, the sibling may have received more genes from the second parent and fewer from the first.

Confused? An article and a graphic in the Genealogy Explained web site at http://bit.ly/2NnKr29 will explain it.

12 Comments

Yes Absolutely and if this site allowed me to post photos I could show you 3 siblings who are all different example:
Sister A Great Britain 34%
Sister B GB 6%
Brother C GB 41%
These are all verified to be full siblings with Ancestry DNA and our other Ethnicity values are just as different. Each child inherits 50% DNA from each parent but there is no telling which 50% each child will get. You each get something a different.

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Dick, This is a good piece because there has been a lot of controversy bantered about concerning differences also differences between samples from the same individual. I must admit, I attended a DNA subgroup session at the Rochester (NY) Genealogical Soc and I understood very little about the material presented and I suspect my knowledge is greater than most. This illustrates a need in my book. Regards, Peter Evans, Wayne County (NY) Historian

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I think that in your synopsis you say a different percentage from each parent. I think that you meant to say a different percentage from each grandparent.

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Martin Harry Watson July 18, 2018 at 9:04 am

I only found this ‘Family History Fanatics’ video today, but it explains all the myths and ignorance about ethnicity estimates. https://www.youtube.com/watch?v=nlmK0X3I1Lo

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    Martin Harry Watson July 18, 2018 at 9:06 am

    Sorry, I clicked ENTER too soon. an excellent presentation, especially the data simulation. It should become required watching for anybody before they give their DNA, hoping to get extreme details of their ethnicity. It counters the YouTube videos of shocked people opening their DNA results on camera. It would also go a long way to explaining statistics to people who shouldn’t be gambling. I will be citing this video frequently. One thing that they don’t mention is the absolute futility of researching your ancestry back more than a few generations because you are eventually going to encounter a non paternal event, i.e. somebody is descended from a secret relationship and this is not recorded anywhere except in your DNA. You only have to go back 5 or 6 Generations, and you have looked at 100 relationships. You only need one man or woman in those 100 or so relationships to have had an illicit relationship producing a child and it makes a mockery of your further research.

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I heard this simple explanation which, while it has some flaws, explains how siblings can be so different. Take a deck of cards and separate the red suits from the black ones. Each color will represent one parent’s potential genetic contribution to a child. Thoroughly shuffle each part of the deck and then deal out half the cards from each half. This represents one child’s genetic makeup. Separate the cards into black and red again and repeat. The second combination may have a lot of cards or only a few cards in common with the first one. For example, let’s say the face cards represent a particular ethnic background-German for example. The makeup of each child’s resulting “genetic hand” can contain from 6 to zero face cards. So a child receiving 4 face cards could show 67% German while one receiving only 1 face card would show just 16% German.

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Our Ancestry may not be reflected correctly by research not just because of a non- paternal event but for a host of other reasons too.. such as a family perished in a disease or Indian raid and one or two young surviving children are taken in as orphans and they are given surname of their new family … or a woman with children becomes a widow or is abandoned and she remarries and her young children take surname of new father.. but just far too often look at all Colonial records about the fallen woman hauled into court for having a child out of wedlock and condemned when the man gets off free!!! Genenealogy is extremely challenging!!!

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Roberta Estes (DNAExplained) points out that ethnic estimates are ONLY accurate on a continent level. Not a country level. Also remember that DNA cousin matches, when properly evaluated with chromosome matching tools (are you paying attention Ancestry?) are quite accurate. Very different from ethnic estimates.

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Time for my beef stew analogy. There is a big pot filled with beef stew which contains beef chunks, potatoes, carrots, green peas and mushrooms. That is your family. Each ladle you take out of the pot is each person in your family. Although drawn from the same pot, each portion has more or less potato, more or less carrot, more or less mushroom and more or less green peas. Some may get NO carrots or NO green peas. Hopefully this helps someone understand the DNA mix. Six full siblings of the same two parents may have very similar results or they could be wildly different.

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I took a genealogy class and in the part about DNA, this over simplified explanation was given. Imagine the letters in your parents names represented their DNA traits. If their names were Robert and Elisabeth, you might receive his dominant traits R & O and E, L, & I from Elisabeth. That might spell Olive or Oliver depending on your sex and what ever trait comes from grandparents Valentino or Victoria. A second child might receive T, H A & S from mom and O from dad and traits from other grandparents Margery (like an M) and Gerald and you end up with a brother Thomas who is a foot taller than you when both are in your 20s. Don’t be surprised if both siblings look alike but with red curly hair compared to dark brown and wavy. Sibling may take on just mom’s or just dad’s traits. I hope that can help someone to at least a basic understanding. Whatever you do, don’t run spellcheck!!!

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I did a DNA test along with 4 of my siblings. I joke that they are not really my siblings because the differences are so great.

For me it is obvious how the differences occur — three of us have a genetic disease from Mom that the others don’t have. I told them we would all be identical twins if we had the same DNA. Even then there would be differences.

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This makes perfect sense when you consider that full siblings often share some physical traits of one parent but not those of the other. In my family of siblings, a few of us have small, narrow heads and angular features like our father but others have larger, rounded heads and softer features like our mother. Two of us have exactly our mother’s hands but only one of us has her eye color. Two are naturally muscular like Mom and the others are lanky and have to work to build muscle definition like Dad. But all of us have Mom’s tooth structure! I would imagine these are some of the obvious visual markers that represent the hidden array of genetic distribution from our parents and grandparents. It also explains why one sibling in our family doesn’t look much like any of the rest of the brothers and sisters but this same sibling DOES look an awful lot like a combination of our Dad’s sister and our Mother’s brother—because we all inherit our grandparents’ and great-grandparents’ traits randomly through our parents.

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