Full or Half: Your Guide to Sibling DNA Test

Full or Half: Your Guide to Sibling DNA Test

  • Chris Powell

DNA tests have helped the long-lost sibling reunion story become a more common reality than ever before. One pair of siblings was reunited 34 years after their separation! 

A DNA test can also help you answer important questions about your family. For example, you can determine if your sibling is really your half-sibling, or not related at all. There are many fascinating surprises a sibling DNA test can uncover!

Ready to learn the answers? We'll show you how it works and what you need to know -- keep reading for more!

Sibling DNA: How Does It Work?

No two people have the same DNA -- not even identical twins (although they share more similarities than most). However, siblings do share enough DNA that a test can determine how likely two people are to be related.

Everyone gets their DNA from their parents: half from their mother and half from their father. However, that DNA gets recombined for each individual, which is why no two people have the same DNA even if they have the same parents.

However, full siblings do tend to share around half of their DNA, which is why sibling tests are so effective. Half siblings usually share around a quarter of their DNA. Although a DNA test can't conclusively prove that two people are siblings, it can give results that are 99 percent accurate.

Which Sibling DNA Test Should You Choose?

There are a few different ways to test whether or not you're really related -- and how related you are. Let's take a look at the types of tests you can choose between. 

Full Siblings

Full siblings share the same two biological parents, while half-siblings share one parent.  

The test to determine full siblingship is conducted when it is known that the siblings share one common parent. To determine whether you're full siblings, the test will look for how likely it is that two people have the same two parents, or not.  Since full siblings share approximately 50% common DNA, we would expect this to be represented in the test.

Half Siblings

A half siblingship test is conducted to determine if 2 or more people share one common parent.  Half siblings should share approximately 25% common DNA. This test will determine whether two people are half-siblings, or not related at all, using a DNA test. 

Siblingship tests determine if there are 0, 1, or 2 common parents.

Why Take a Sibling DNA Test?

Is a sibling DNA test worth it? Let's take a look at some ways answering these family questions might benefit you.

Find a Lost Sibling

Taking a DNA test can help you confirm if someone who you think might be your sibling really is. But can it help you find a sibling that you never knew you had?

Although the chances of this occurring are slim, it's certainly not impossible. Your lost sibling simply needs to have taken a DNA test within the same database as yours, so their results will come up as a match. If they're in a different database, it won't work.

Get the Answers

If you and your sibling (or supposed sibling) have long suspected there's more to the story than what your parents told you, a sibling DNA test can help you get the answers. This can clear up questions that seem otherwise impossible to answer.

Even standard DNA tests can raise some questions. Because our DNA gets recombined for each individual, a pair of siblings may get very different results from an ancestry test. If those results are too different, you might find yourself wondering if you're really siblings at all.

Figure Out Estate Questions

Sometimes, a DNA test can help navigate issues surrounding an inheritance or estate. For example, you may want to write your full sibling into your will, but finding out that you're not actually related could change that.

How a Home DNA Test for Siblings Works

Ready to take the test? Let's find out what's in store after you've made your decision.

If you buy a test for home use, you and your sibling will each receive your test in the mail. You'll use what's included to gather a sample of cells from the inside of your cheek. This process is fast and painless.

Follow the instructions to put your cell sample in the provided container and mail it off to the lab to get tested.

If you know that you have at least one parent in common, it's also helpful to get a cheek swab sample from that parent, if possible. This can help give more accurate results. 

Once the lab receives your samples, staff will analyze the samples to find the relationship between them. You'll get the results back in a matter of days, along with information on what your results mean for your sibling relationship.

The more DNA markers the test analyzes, the more accurate it will be, so make sure to look for a test that analyzes more markers. 

Is a Sibling DNA Test Right for You?

If you want to know the answers to questions about your sibling relationship, a sibling DNA test is the only way to get them. 

These tests have granted people the freedom to get their own answers, rather than relying on what their parents say. If you think you want a test, don't hesitate to get started: it's an easy process that delivers fast results.

Ready to take your test? Click here!