DNA Testing

Sibling DNA testing can confirm a biological relationship between siblings. Also, we can determine if the relationship is one of full or half siblings. Furthermore, it is also possible to say if people are unrelated.

The Sibling DNA test is used to answer questions such as:

  • Do we have the same father?
  • Are we full siblings or half siblings?
  • Are we half siblings or unrelated?
  • We have the same mother, but do we have the same father?

Situations vary, and family circumstances can lead to the use of a Sibling DNA testing. Also, ages of people taking part can range from new-born babies to participants over the age of 90.

How Sibling DNA testing works

We use the DNA samples taken from mouth swabs to generate a DNA profile for each test participant. Next, we compare the DNA profiles and determine the likelihood of a relationship. In other words, the likelihood that the participants are biologically related. This can be as full siblings, half siblings or unrelated.

The test works on the fact that a child inherits half of his or her DNA profile from each of their parents. For instance, half the child’s DNA profile matches their mother and the other half matches the father. As a result, the DNA of full and half siblings will show an increased amount of genetic material in common. In comparison to when compared to the DNA of unrelated individuals.

This statistical analysis takes into consideration many different factors. These include the number of matches between the DNA profiles of each person. Also, this includes how popular DNA markers are within a given population and ethnic group.

We use the values from the calculations to generate a percentage probability. This will show which relationship is most likely to exist between the individuals. For example, take two individuals who want to know if they are full or half siblings. This percentage probability will show which relationship is most likely to exist.


What is the Accuracy of the Sibling DNA Test?

Sibling DNA tests are very accurate. We achieve conclusive DNA results in over 96% of test cases*. But, as with any DNA test of this type, there is a small chance that the test will yield an inconclusive result.

Inconclusive results are not the same as negative results. An inconclusive result means that the analysis cannot provide an answer to the question asked. Inconclusive results occurs in less than 4% of Sibling DNA tests*. Causes of inconclusive results in include:

  • The DNA markers that show matches between test participants are very common in the general population. As a result, the matches do not provide enough evidence to confirm if a biological relationship exists.
  • There is a lower level of DNA matches than expected. This is due to the chance nature of inheritance in families.
  • Where matches may have occurred, mutation has changed the DNA marker. As a result, this can cause mismatches at further locations within the DNA profile.

*Conclusive results in over 96% of Full Sibling DNA tests when the biological mother is included in the test.


When should other forms of DNA test be used?

The reasons for taking part in a Paternity, Sibling or Grandparent DNA test, are usually very similar. First is that there are potential biological relationships that exist between test participants. Second is that the evidence to support that biological relationship does not exist. In other words, the evidence is lacking or has been brought into question.

In the UK, the identity of a person’s biological mother is rarely questioned. So, DNA tests are used to gather evidence relating to the paternity (biological father) of one or more of the test participants.

To extract as much information from a DNA test, it is important to test the most direct relationship possible. For example, a test between parent and child, will always produce more conclusive results than a complex test. For instance, tests such as Sibling or Grandparent, test for relationships further removed from a direct genetic link. These tests can be very accurate. But, they cannot replace the tests that directly analyse and compare the DNA of a potential biological parent.


For example, a male and female believe they may have the same biological father. They know that they have different biological mothers. If the alleged father is available to take part, then we would recommend a Paternity test.

What is the alleged father is not available? The parents of the alleged father (the potential paternal grandparents) can take part in a test. As a result, the Duo Grandparent DNA Test would be the next test recommended.

Furthermore, what if a DNA sample is available from one or more of the participant’s biological mothers? In this case, then we would recommend a Sibling DNA test or a Single Grandparent DNA test.

These tests can also be performed without the inclusion of a DNA sample from the mother(s). But a DNA sample provided by the mother would increase the information provided to the lab for analysis. We would recommend this as it will increase the chance of a more conclusive DNA test result.

Please note. Complex tests such as Sibling or Grandparent DNA Tests, will not state the identity of alleged biological parents. In other words, the alleged father will not be stated in the DNA test report.