A sibling DNA relationship test is performed to establish if two or more suspected siblings share one or both parents. These tests are typically used as an indirect method to prove family relationships when a potential father is not able or unwilling to undergo paternity testing. While less common, a person can also utilise a sibling DNA test to determine if two people have the same mother.

Connecting Families with a Sibling DNA Relationship Test

Hundreds of stories about siblings finding each other through DNA testing are published online. While these discoveries can be emotionally intense for all parties involved, many people are grateful for the chance to bond with newly-discovered family members. Some examples include:


  • Four women who looked alike and had similar mannerisms discovered they were siblings. Each of the women already had a sister they had grown up with. Two of the “unrelated” women met after a mutual friend told them how much they resembled each other. DNA testing revealed that all four women were born to the same mother, who had put twin girls up for adoption. Later in life, the mother had two more daughters.


  • DNA testing revealed that Ashley and Latoya, who were best friends for 17 years, were half-sisters. They had the same biological father, who was just as delighted by this discovery as his daughters were.


  • When ancestry DNA testing revealed what they thought was a first-cousin match, Julie connected with Robert online. Robert’s biological father confirmed that he had gone out with a 16-year-old girl in secondary school with the same name as Julie’s birth mother. Julie and Robert agreed to take a half-sibling test, which confirmed they shared the same biological father.

Types of Sibling DNA Tests

Full Siblings vs. Unrelated

The DNA of two individuals is compared to calculate the probability they have the same biological mother and father versus being completely unrelated. An everyday use for this DNA test is in immigration cases where an individual wishes to sponsor a possible sibling applying for a UK visa or passport.

Full Siblings vs. Half Siblings

The DNA of two individuals with the same biological mother is compared to establish the probability they have the same biological father. It is recommended that samples from the birth mother are also tested. Doing so can help identify precisely which genes the two children inherited from their biological father, thereby increasing the conclusiveness of the test.

Half Siblings vs. Unrelated

The DNA of two individuals with different biological mothers is compared to determine the likelihood they have the same biological father. Similar to cases where siblings share a biological mother, it is recommended that both biological mothers participate in this test.

Reasons to Perform a Sibling DNA Relationship Test

There are several reasons why a person might need a sibling DNA test, including:

  • Confirming biological relationships, which can be crucial in adoption cases
  • Revealing inherited health risks, helping to map out a family’s medical history
  • Assistance with legal matters like inheritance claims, insurance claims, and immigration cases, where proof of family ties is often necessary
  • Supporting government benefit claims, where proof of a biological connection might be required

Sibling DNA Testing: A Valuable Research Tool

Sibling DNA testing is an essential resource for researchers in various scientific communities. Testing can help explain the genetic nature of diseases and their correlation with other influential factors, such as environmental exposure. 

Regardless of why you choose a sibling DNA test, selecting a highly-trusted and accredited lab is crucial. DNA Diagnostics Centre (DDC) offers the latest technology and accurate testing to resolve questioned biological-sibling relationships for legal and peace of mind purposes.


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