brother sister DNA

How accurate are sibling DNA tests?

How accurate are sibling DNA tests? How does the test work? How long do you have to wait for the results? Read on to find out…

How accurate are sibling DNA tests?

AlphaBiolabs is an ISO 17025-accredited laboratory, meeting the very highest international quality standards. Our expert DNA scientists ensure that your DNA tests are accurate and performed to the highest specifications.

AlphaBiolabs analyses up to 42 DNA markers in its relationship testing services. In the case of paternity and maternity DNA testing it is usually possible to provide conclusive results. If a biological parent is undergoing DNA testing, both parent and child will share identical sections of DNA at each marker. It is therefore possible to identify which half of the child’s DNA is inherited from the mother and which half is from the father.

Sibling DNA tests are more complex, depending on whether the tested individuals are full siblings or half siblings. A full sibling has the same biological mother and father and is a first-degree relative. On average, full siblings share 50% of their DNA. Half-siblings share either a mother or a father, are second-degree relatives, and have around 25% overlap in their DNA. Sibling DNA tests can thus test individuals to establish whether it is more likely that they share both parents, have one parent in common, or are unrelated.

Across the DNA testing industry, sibling testing can be up to 40% inconclusive. AlphaBiolabs has been able to reduce this inconclusive rate down to 24%. However, should you use our sibling DNA testing service and not get a conclusive result, we guarantee to refund the price of your sibling test. That’s a promise.

How does sibling DNA testing work?

Full instructions on how to collect a DNA sample from both siblings is included in the testing kits. This is a simple process and just involves rubbing the inside of their cheeks with a mouth swab to collect cheek (buccal) cells.

When these swabs are returned to our laboratory, the DNA is extracted from the cheek cells. Our in-house DNA experts then use statistical analysis to evaluate the amount of DNA shared between the siblings, and the frequency of the observed DNA within the relevant population. Full siblings are expected to have more DNA in common than half-siblings, and half-siblings normally share more DNA than unrelated individuals.

Further details on AlphaBiolabs’ sibling testing and other DNA testing services can be found on our website. Alternatively, please call us on 01 402 9466 or email us at

Order a Sibling DNA test

Buy an AlphaBiolabs home Sibling DNA Test now for just €229.