Do Brothers And Sisters Have The Exact Same DNA?

Wny Siblings Do Not Share The Same DNA

I have five sisters and when each of us take genealogy DNA tests we all have a different result. This is because when it comes to tracing your roots through a DNA genealogy test, biological siblings may find that they have much less DNA in common than what they thought.

On average brothers and sisters only share about 50% of the same DNA. When the sperm and eggs engage to form a human embryo, reshuffling or genetic recombination takes place. Simply, you can inherit different DNA from your mother and your father but it is not always equally split as 50-50.

So in reality two siblings can both take a DNA test and find that they only share 50% of the same DNA. Even the results they get from a genealogical DNA test can also be different.

The DNA 50 -50% Myth

As my mother was born and raised in Stockholm Sweden we assumed that my DNA would show that I was 50% Swedish. But that is not the reality because of the way DNA is reshuffled.

In fact, even my mother’s own genealogy DNA test does not show her as 100% Swedish but with some Russian and Finnish ancestors. In doing our genealogy research we have not been able to find any ancestors that are not Swedish.

Does this mean that the genealogy DNA test is incorrect? No, the test is most likely correct but it could just mean that she has received some DNA from an ancestor that may go so far back that she doesn’t even know about them. It doesn’t mean that she is still not 100% Swedish.

This is the 50-50% myth with the genealogy DNA testing. Most people assume that when they get the test if one parent is 100% Swedish and the other parent is 50% British and 50% German that the DNA test would show the ethnicity results as 50% Swedish, 25% British, and 25% German.

The 50 -50% genealogy DNA testing myth is just that – a myth. The truth is that our DNA is more like a kind of DNA game of chance as the DNA is reshuffled in what is known is DNA genetic recombination.

DNA Reshuffle

When two siblings, even fraternal twins, have different DNA results this is not due to a family secret that has been hidden in the closet or that it was the “milkman” after all. But instead, this is due to DNA reshufflings or genetic recombinations.

DNA genetic recombinations are when genetic material is exchanged with different organisms. This exchange of different organisms leads to the production of the offpsring with unique traits and DNA that will differ from either parent.

When the body creates sperms or eggs the chromosomes are divided. These chromosomes will exchange genetic information with each other. Once the sperm and eggs mature into a human embryo, the embryo will have its own unique DNA.

Two siblings may look similar, but their genetic DNA may not be exactly the same. Siblings will share at least 50% of the same DNA but they will have a different genetic DNA combination that they receive from their parents.

The exception to this is some identical twins that can share the exact same DNA. Fraternal twins will have different DNA. This is because each person will have their own unique DNA footprint due to the genetic recombinations.

Even though siblings may have different DNA genetic combinations from their parents this doesn’t mean that they are not related. Biological siblings may not have the exact same DNA but they do share the same family tree, the same parents, and ancestors.

Different DNA Tests and Different DNA Results

To add to the confusion, someone may do a test with several genealogy DNA companies and find that the results they receive are all different. The reason for this is that the DNA companies will use a DNA chunk from the database of people that they have.

This is because each genealogical DNA testing company will have its own reference panel and algorithms. So you are likely to get different ethnicity results from each company according to which data they presently have.

In reality, this means that your results can differ according to what data the company you are doing your genealogy DNA with have. That is why many genealogists recommend that when you do DNA testing that you may want to consider doing it with several companies so that you can compare the results. Not all the results you get will be exactly the same.

Furthermore, the genealogy DNA companies will tell you that their ethnicity tests are only suggestions. This means you should look at the test and use the tests as a guide only. You should do your own research to back up what the genealogy DNA tests are telling you.

If you are adopted and are trying to find your biological parents we would suggest that you may try to take a few DNA tests to see if you can find any biological relatives. This is because the data that the DNA companies have to match you with your relatives will only be the data that others have given to them through their taking a DNA genealogy test.

The more tests you take the better the chance you will have to be able to find a match of biological relatives or a relative you did not know. This is because you’re dependent upon what information each DNA genealogy testing company actually has.

Also if your relatives are from Asia, Africa, or other parts of the world where DNA genealogy testing may not be very popular you may find that you do not receive many results of biological relatives. But, as these parts of the world start to have more DNA genealogy testing you may find that you will be able to find biological relatives sometime in the future.


So if you and your siblings all decide to take a DNA genealogy test and you find that you only share 50% of the same DNA, know that this is completely normal. Yes, you are still related. Yes, you still share the same family tree as it is completely normal for siblings to share 50% common genetic DNA.

Related Questions

What Are The Genealogy DNA Tests?

We inherit our DNA from our parents and our ancestors. Genealogy genetic ancestry tests are very useful in finding out more about our ethnic heritage, health traits, and ancestors. Most tests given are for Y-DNA, mitochondrial DNA, and autosomal DNA. There are now 5 major DNA companies that are performing genealogical DNA testing.

You can find out more by reading out blog Genealogy DNA Tests and Testing – Read This Before You Buy by clicking here.

Why is Ancestry Travel the New And Exciting Travel Trend?

Ancestry travel is a new and exciting way to travel as it helps you discover your family history. The ancestry travel trend has been driven in part by the at-home DNA testing, people wanting to travel with meaning, and a new perspective about life. Ancestry travels helps you feel a connection with the place you are traveling and your also ancestors.

You can find out more by reading our blog Why Ancestry Travel is The New and Exciting Travel Trend by clicking here.

Anita L Hummel

Hi, I live in Hanoi, Vietnam but spend time traveling the region. I love to share with you things I see and learn through my travels.

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Wny Siblings Do Not Share The Same DNA