Can a DNA test determine if siblings have the same father?

The answer to this often asked question is YES!

Most of the time a sibling DNA test is done for the specific reason to determine paternity. Paternity testing determines whether or not the two, or more, individuals have the same biological father.

Yes! Most of the time a sibling DNA test is done to determine paternity. Paternity testing determines whether or not the two, or more, individuals have the same biological father. Maybe times the possible father has died, or he may be incarcerated, or is unwilling or otherwise unavailable to take a paternity test. These are the situations that sibling DNA testing was designed for.

A sibling test is usually done to put a person’s mind at ease, as the question about who the biological father is does not really go away until it is answered. However, there are also times that sibling test can be done to determine if a biological father is the same between two or more people for legal reasons. Because a legal sibling DNA test is highly accurate, the results can be used to establish a paternal relationship of children, by a mother, to obtain Social Security survivor benefits for their child. In such cases, the biological father of one child is undisputed and the mother needs to prove that the other child has the same father. Sibling DNA tests are also frequently performed to provide evidence of biological relationship for U.S. immigration applications. In rare cases, such as those where a child was given up for adoption, a sibling test may also be performed to address whether another individual has the same biological mother, known as a maternal sibling test.

Only companies whose sibling testing provides the same answer on a sibling DNA results report, whether the test was done for private reasons or legal reasons, should be used to ensure the results are accurate .

Two type of sibling test exist:

Full Siblings or Half Siblings? In this sibling test, we are determining if two siblings who have the same mother also have the same father. The DNA of two individuals with the same biological mother are compared to determine the probability that they have the same biological father. For these tests, it is always helpful when samples from the biological mother are included to also be tested. This enables the lab to determine exactly which genes the two children inherited from their biological father and thereby greatly increases the conclusiveness of the test.

Half Siblings vs. Unrelated? In these sibling tests, the DNA of two individuals with different biological mothers is compared to determine the likelihood that they have the same biological father. For these tests, we recommend that samples from one biological mother (it does not matter which one) be tested if possible. This enables the lab to determine exactly which genes the two children inherited from their biological father(s) and thereby greatly increases the strength of the test.

When the suspected father is not available, and you need to know the answer as to who your biological father is, you can be assured that a sibling DNA test is one option that is accurate and easy to do.