DNA Testing Siblings Accuracy

December 30, 2017

Sibling DNA testing is designed to determine whether two or more individuals share a biological parent or parents and results in confirming full siblingship, half siblingship or the absence of any biological relationship. It is currently the most accurate and reliable method for confirming or negating this biological relation, made even more attractive by modern at-home testing options and their budget-friendly prices. 

If you’re thinking about performing this test but aren’t quite sure about the accuracy levels of the entire process, read this post and find out more about the science behind sibling DNA testing and its overall reliability. 

DNA Testing Siblings Accuracy

Solid Numbers

Right off the bat, we’ll deal with the exact numbers when it comes to the accuracy of sibling DNA testing. Of course, different companies offer different testing solutions, use different testing methods, feature more or less modern processing labs, and have different professional teams, which all has its impact on the overall reliability of the test. The most prominent providers on the market feature testing options with 99.99% accuracy when confirming a biological relationship and 100% when excluding it.

It all comes down to determining the so-called siblingship index by inspecting a certain number of genetic markers and comparing them between the test subjects. Naturally, the more genetic markers tested by your provider of choice, the more genetic material will be compared, yielding results with a higher accuracy coefficient. Renowned companies usually check around 10 markers or more. Still, we have to be aware that sibling DNA testing deals with percentages of likelihood, not solid absolutes. This is why you’ll never see a respected company claiming 100% accuracy for any of its relationship DNA tests. Consequentially, if your siblingship index is greater than 1.00, the likelihood of full (true) or half siblingship is extremely high. If it’s lower than that, however, that likelihood goes in the other direction.


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