5 best home DNA test for siblings : guide


Have you ever wondered if you share the same biological parent and DNA with your sibling? The DNA sibling test can reveal unsuspected truths about your family history. Dive into the history of genetics with us to find out how this DNA test works and what it can reveal.

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  • Family Tree DNA: best DNA test that establishes sibling links on both sides of the family by analyzing maternal and paternal haplogroups
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Fraternity test: an exam to prove blood ties between brothers and sisters

The fraternity test is a genetic analysis that examines specific markers in each person’s DNA. This test is used to determine whether two individuals are biologically brothers or sisters. The fraternity test differs from the paternity DNA test and the maternity DNA test, which compare a child’s DNA with that of a presumed parent to find the parentage link.

Why perform a sibling test?

Conducting a fraternity test is of the utmost importance, and proves useful on several levels.

For legal purposes, it can be used in situations such as inheritance disputes and child custody rights. The test also proves useful for immigration procedures or to prove the existence of a biological relationship.

From a medical point of view, this test can help you find out about your family ties. It can help you understand your family history, particularly with regard to genetic diseases. 

The need to know your origins, to reconnect with a lost family or simply to confirm doubts can also be a reason to perform a fraternity test. Also, a fraternity test can serve as an alternative to establish a paternity link in the absence of the presumed father.

The different forms of fraternity tests 

The complete sibling test

The full sibling test analyzes the DNA of two individuals to determine whether they share the same biological father and mother. It is particularly useful when both parties wish to confirm that they are full siblings, sharing 100% of their genetic heritage.

The half-fraternity test

The half-fraternity DNA test is used to demonstrate the common parentage (whether father or mother) of two people. This test is often requested when it is suspected that two individuals could be half-siblings, and share 50% of their DNA.

The unrelated half-fraternity test

This test analyzes DNA to demonstrate that two people considered half-siblings have no biological connection. It is useful in situations where there is doubt about the sibling relationship. It eliminates any possibility of a genetic link between the two parties.

Who can participate in the test?

The sibling test generally involves the participation of two or more individuals assumed to be siblings. For a test between two brothers or half-brothers, Y-chromosome testing is recommended to achieve 100% accuracy for paternity exclusion. Mitochondrial DNA testing can also be useful for proving maternal parentage.  

In a half-fraternity test, the participants are two people who believe they have a single parent in common. Sometimes, to increase the accuracy of the test, it can be beneficial to include DNA samples from one or both of the presumed parents. Samples from other family members (uncles, aunts, grandparents) may also prove useful.

How is a sibling test performed?

The process of performing a sibling test involves several steps.

  1. Sampling: You will receive a sampling kit at your home. Using the swabs, rub the inside of the cheek to collect DNA-rich buccal cells. Non-standard samples such as hair, nails or toothbrush can also be used for DNA analysis. 
  2. Send to lab: Once samples have been collected, place them in special envelopes provided. Then send to the laboratory for analysis.
  3. Sample processing: in the laboratory, DNA is extracted from buccal cells and purified. It is then analyzed to identify specific genetic markers. Scientists compare genetic profiles to assess the likelihood that participants share a biological link.
  4. Results report: a detailed report is generated, indicating whether or not a biological link exists as siblings, half-siblings.

Interpreting results

How to read test results

The results of a fraternity test are structured in a table:

  • Each column represents a participant.
  • The rows detail the genes to be analyzed
  • The genetic structure is indicated by one or two numbers for each profile.

The results of the sibling test often indicate a percentage probability that participants share a biological link. A percentage above 90% strongly suggests a sibling bond. If this percentage is low, it indicates that they are unlikely to be biologically related. 

Some reports may also include a “brotherhood index”. A value greater than 1 indicates the likely existence of a biological link, while a value less than 1 suggests the opposite.

The case of false positives and false negatives

A false positive indicates that two individuals share a biological link, when in reality they do not. Conversely, a false negative occurs when the test falsely suggests that there is no biological link between two people, when in fact they are related.

These errors can result from a number of factors, such as laboratory errors, sample contamination or chance genetic similarities. For this reason, we recommend that you carry out these tests in reputable laboratories. You may consider retesting in case of doubt or ambiguous results.

Is this type of DNA analysis accurate?

Thanks to technological and scientific advances, fraternity testing analyzes and compares thousands of genetic markers. As a result, it generally offers a high level of accuracy. However, the reliability and authenticity of the test depend on: 

  • Sample quality
  • Analytical laboratory accreditation 
  • The number of genes compared (on average 15 to 22 alleles) 

An ISO 17025-certified laboratory can perform a test with an accuracy of over 99%. You can ask the laboratory for a more extensive search of the number of STR Loci to improve the accuracy of the test.

Legal and ethical implications of the fraternity test

Fraternity testing, while a powerful tool for determining family ties, raises important legal and ethical issues. The results can influence decisions in areas such as custody rights, inheritance disputes or immigration procedures. 

For a fraternity test, the participants’ consent is mandatory and must first be obtained in writing. Without it, carrying out a test or disclosing the information may constitute a breach of privacy. For minors, consent must be given by one of the legal parents.

Personal data must be protected and kept completely confidential by laboratories. Moreover, in some countries, the fraternity test is prohibited by law. It can only be undertaken for medical, judicial or scientific purposes. For this reason, most tests are ordered from laboratories online.

What’s the price of a brotherhood test?

The cost of a fraternity test varies according to the type of test (home or legal), the laboratory chosen and the speed of the result. The price of the test generally hovers around 300 euros for the participation of two people. You can also find tests between 99 and 200 euros. In addition, sibling tests are not reimbursed by insurance.

The final word on sibling DNA tests

Fraternity testing reveals the mysteries of our family heritage with remarkable precision. Whether confirming biological links, resolving legal disputes or understanding our own history, these tests play an invaluable role. That’s why it’s important to choose a certified laboratory for accurate results.