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Why Should I Ask Other Relatives to do a DNA Test?

If you have tested your DNA, should your other relatives test theirs, too? This article will explain how and why having multiple family members test their DNA can help you learn more about your ancestors.

“I’ve already done a DNA test.  Why should anyone else in my family do one, too?”  Does this sound like you, or anyone that you know? 

Here’s a hint:  The more people who test, the better!

Why Should I Ask Other Relatives to do a DNA Test? Featured image with graphic of multiple generations of a family

In this post, you will learn:

  • Why it’s a great idea to get your parents to do an autosomal DNA test
  • How it can help to get your siblings to test, if your parents can’t or won’t test
  • The benefits of having other relatives test, especially older relatives

What Can I Learn From Having Other Family Members do a DNA Test?

You can learn more detail about your family’s ethnic background

Each generation, some DNA is “lost” (i.e. not passed down to the next generation).  Also, siblings and cousins all inherit different DNA from their parents, and will share some DNA with their grandparents and great-grandparents that their siblings and cousins don’t have. 

Testing multiple family members allows for a more complete “picture” of the family’s ethnicities.

You will find new DNA matches

Your family members will have DNA matches that you don’t have, and those people are still related to you!  By finding these new family members, you will be able to learn more about your family tree.

You will be able to confirm family relationships 

Families are complicated, and sometimes we learn through DNA testing that someone is a “half” sibling, or that our great-uncle was our grandfather’s “half” sibling.  This can be a pro or a con, but it’s good to know that this is the type of information that you may learn.

Why Should My Parents Do a DNA Test? Don’t I Have All of Their DNA?

Here’s one thing that might come as a surprise:  Your parents didn’t share all of their DNA with you!  You got 50% of your DNA from each parent, but there was 50% of their DNA that you didn’t get.

There isn’t any way to determine which 50% you get, and unless you are an identical twin, your siblings didn’t get the exact same 50% that you got.  That’s a lot of getting, and gotting, but stay with me.

Even if you have five siblings and they all did a test, there would still be DNA that your parents had that no one inherited.  You can thank statistics for that. 

So if at all possible, doing a DNA test on one or both of your parents is the first thing that you should do.

Below is a simplified graphic that can help you visualize the concept that you don’t inherit all of your mother or father’s DNA, and your siblings don’t inherit all of the same DNA that you do.

How DNA is Inheritd From Parents

You can see in the graphic above that some of your circle overlaps with your siblings, but some of it doesn’t.  It’s just like that in your DNA:  You share some of your DNA with your siblings, but you inherited DNA that they didn’t, and vice versa. 

The solution of getting your parents to do a test eliminates this issue.

(The only flaw in the graphic is that Siblings #1 and #3 don’t appear to share DNA.  In a real scenario, all siblings share a sizeable amount of DNA with each other inherited from BOTH parents. 

I just thought it would look funny and crowded if I tried to illustrate that in such a small space, ha!)

As an added benefit, if you got both of your parents to do a DNA test, then your siblings don’t really have to do one (unless there is a reason to think that you are not full biological siblings).

Click here to buy the Understand Your DNA Results Ebook

Testing Your Siblings Can Be Helpful

If your parents are no longer with you, or they are not interested in taking a DNA test, don’t worry.  If any of your siblings are interested in doing a test, their results will show many things that yours do not. 

Obviously, if we can’t test our parents, our siblings are the next best thing!

Check out this graphic that illustrates how your sibling has DNA from your dad that you don’t:

Why Does My Sibling Have DNA That I Don't Have

Asking Older Relatives to Test is the BEST

One of the best gifts that an older relative can give to you, and future generations, is a sample for a genetic DNA test.  A test from your grandparents, great aunts or uncles, or another older relative can help you “reach” back further into history. 

Their test results will show DNA that wasn’t inherited by your parents, and thus couldn’t have been inherited by you.

In the case of a great aunt or uncle, their results will reveal DNA that your grandparents didn’t even have!  It’s kind of like a puzzle, and the more pieces that you can add to it (in the form of DNA tests for all of the previous generations in your family), the better picture you will have of where you and your family came from.

Your older relatives will also have different DNA matches than you, since some DNA is lost over the generations.  Those DNA matches could help you piece together how you are related, and also add information to your family tree.  Amazing!

Below is an infographic (feel free to share!) about the benefit of asking your older relatives to do a DNA test.  I’ve had very good luck with this in my family. 

My grandmother, her brother, and my grandfather’s brother have all tested, and it has been very enlightening.  I wonder what you will find in your family?

(Click Infographic to Englarge, Right-click to download)

Share this Image On Your Site

Do you need to order more tests?

If you have decided that you are ready to move forward with asking additional relatives to test, but you’d like to purchase the test yourself (sometimes this is the only way we can get certain relatives to agree!), I recommend testing with Ancestry DNA, 23andMe, Family Tree DNA or Living DNA. 

It’s best to test your relative with the same company that you used, since you can see Shared Matches, or matches that you have in common with your relatives.  This helps you narrow down which line of the family other DNA matches are on, and can really help with research.


Thank you so much for stopping by and reading my article on this topic.  I would love to hear from you in the comments if you have any thoughts or questions on why it is beneficial to have your relatives do an autosomal DNA test.

Share the knowledge!

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