Individuals who share both biological parents are called: full sisters and brothers. They have in common about 50% of their genes .
Individuals who share only one biological parent are called half-siblings . They have in common about 25% of their genes .
When the number of sibling participants is greater than two, you must choose a main participant who will be the only one compared to the other two . The choice of participant depends on your research on the relationship between the individuals. . Inform the laboratory before, as they may charge you an additional cost.
It is always recommended to test one or both of the known parents to get the most accurate results possible, since the genetic heritage of children is only half of that of the parents.
The parents' participation in the sibling test makes it possible to exclude half of the child's DNA leaving the other half for comparison with the DNA of the person sought. This improves the reliability of results .
If in your research of kinship, the doubt relates to presumed parents coming from the same family, then all the known relatives must take part in the test with the children, otherwise, the results may lose precision. As a general rule, the more genetic information available, the better the chances of a successful test.
Can siblings' DNA test results be used for legal reasons?
Yes, sibling DNA test results can be used for administrative or legal proceedings such as immigration, social security benefits, inheritance rights, etc. More information about the legal tests . In contrast, a report for a private home test cannot be used legally.
How does this test work if you don't know the relationship between the participants?
If it is unclear whether the possible brother or sister is a half-brother / half-sister or "complete", we first check whether there is a biological relationship between them. If not, the test is terminated. If a relationship is determined in an initial report, then the lab may continue the DNA study to determine the full relationship between the participants.
How do you understand the results of a sibling DNA test?
Understanding the results of a sibling DNA test is a bit tricky, as there can never be a definite "yes or no" answer since it is considered an indirect test. More information on understanding indirect testing . Calculations for relationships such as grandparents, aunt and uncle, and siblings all involve statistics, and a relationship probability is given as a percentage in the report:
- 90% or more: the biological relationship is sustained
- Between 9% - 89%: the result is inconclusive, in this case additional people must be tested
- Below 9%: the biological relationship is excluded
Can we test from different addresses?
Yes, labs always offer an option to send you multiple kits if participants are unable to test together. This can also be done even if the participants are in different countries.
Can we come to the lab for a test?
Generally no, the companies that offer you online tests are merchant companies that work in partnership with the laboratories to relocate all the logistics of the procedures and the customer service. This allows the laboratory to concentrate solely on the work of analysis and thus it is very rare that they provide a place open to the public. In addition, the sample collection that is requested does not require the intervention of a professional.
Can taking medication or drugs affect a DNA test?
No, no substance can alter a person's DNA. But the samples you send to the lab can be contaminated or degraded by many environmental factors. Take care to keep them in paper envelopes, avoid handling them with your fingers, and above all do not use a plastic bag.
Frequently Asked Questions
Paternity search between brothers
The analysis of the Y chromosome makes it possible to define whether the two brothers or half-brothers come from the same paternal line. By deduction if they have the same biological father
Paternity search between sisters
The analysis of the X chromosome makes it possible to define whether the two sisters share the same paternal X chromosome. For this, it is mandatory that the sisters share the same biological mother.
Relationship DNA testing compares the genetic profiles of two or more people to determine a common biological heritage. In general, the test highlights the similarities and differences that make up your genetic fingerprint and evaluates your match rate in order to give you results corresponding to your search for a relationship.
Under no circumstances can this study be established without comparing different individuals , because your DNA is unique and does not contain the genetic profiles of your family, but only its heritage.
The DNA Relationship Test
You want to remove any doubt about your biological origin or that of a loved one? But you don't know which test is best suited to your situation? Follow our guide! On infotestadn.com, we you propose to guide you on the possible tests available by putting you in the position of a search for paternity or maternity . It's simple and free, which allows you to already have solid information before contacting the laboratory that suits you.
Which DNA test to choose?
Sibling DNA testing can be done with:
- Saliva samples (sterile buccal swabs)
- Non-standard samples: Like hair, nails, toothbrush...
Be careful, you must follow the instructions and respect the conditions so that the samples provide enough genetic information for your test.
What type of sample is used for the test?
Sibling Test Participants
- One or more brothers can participate
- The test can be done between half-brothers
- For a paternity search between two brothers or half-brothers, it is advisable to use:
which in this case is much more reliable
- One or more sisters can participate
- The test can be done between half-sisters
- For a maternity search between two sisters or half-sisters, it is advisable to use:
which in this case is much more reliable
Types of Sibling Tests
The Complete Sibling Test
In the full sibling test, the DNA of two people is compared to determine the likelihood of them having the same biological mother and father, versus being completely unrelated .
The Half-Sibling Test
In the half-sibling test, the DNA of two individuals with the same biological mother is compared to determine the probability that they have the same biological father or vice versa .
Labs always recommend testing samples from the known biological parent to increase accuracy.
The Unrelated Half-Sibling Test
In this sibling test, the DNA of two individuals with different biological mothers is compared to determine the likelihood that they have the same biological father or vice versa .
Labs recommend to test samples from one, preferably both, known biological parents to increase accuracy.
There are 3 different statistical analysis that can be performed during sibling DNA testing which are based on the status of the participants according to the family situation.
DNA Test Results
The reliability and authenticity of test between siblings depends on several factors:
- Sample quality
- Laboratory accreditation
- The choice of the test according to the family situation
How reliable are the results?
The quality of the DNA will depend on the collection and storage of the samples . It is therefore important to follow the instructions of the laboratory in order to ensure that you receive results.
Accredited laboratories meet the requirements relating to the analysis process, management of resources and equipment, impartiality and confidentiality of information. For a sibling test, the laboratory must have ISO 17025 accreditation .
The reliability of the result depends on the number of genes compared. All the laboratories offer tests on an average of 15 to 22 genes (Loci STR) to make the comparison between the participants. Depending on your situation, you have the possibility to ask the laboratory for an extended comparison of the number of loci. The extended comparison improves the precision and therefore the reliability of the results.
The results are presented in the form of a table:
- Each column corresponding to a participant
- Each line to the genes to compare
- The composition of the gene is represented by one or two numbers on each profile
How do I read the results of a sibling test?
Sibling DNA analysis is an indirect relationship test. The genetic laboratory tries to recreate the profile of a father or a mother with, as information, only those of the children. Thus the test is based on statistics and probabilities that play an important role in the interpretation of results. Participants may have alleles that are different due to random, yet common, inheritance. Conversely, it is not because the alleles are similar that they necessarily come from the parent in common.
It is possible to obtain inconclusive results .
Checking the participant relationship:
The sibling DNA test comes with a relationship index . This index on base of 1 expresses the probability of genes in common between the participants. The relationship index is then converted to a relationship percentage.
The sibling test results should be interpreted in terms of probability and the sibling relationship index is translated into a percentage that can range from 0% to 99.99% .
- If the index is greater than 1 and your percentage is greater than 90%, the test is positive
- If the index is less than 1 and your percentage is less than 10%, then the test is negative
The choice of laboratory is a very important step when you want to do a sibling test. You should know that each of the laboratories has specific services that are useful depending on your situation.
The choice of a laboratory can be made according to:
- Your family situation and available participants
- The confidence that the laboratory inspires through customer feedback
- The transparency of the company concerning its activity and your expectations
How to choose a reliable Laboratory?
Order your DNA test kit online
Receive your DNA kit at
Discover your results
The Sibling DNA test determines the likelihood of siblings being biologically related by a biological father and mother.
The analysis is a genetic comparison between the genetic profiles of two individuals in order to establish a parental link to define if statistically, the parties share the same two parents, one parent or have no parent in common.
What is a Sibling test?
The vast majority of the answer is no ! Genetic analysis to determine parentage becomes too complex when the presumed father or mother is already a member of your family . As your DNA is composed with genes equivalent to your cousin, you have a good chance of receiving a positive, but not conclusive, result. Which means that your biological relationship is proven, but it cannot accurately answer your doubt of paternity or maternity.
Can I take a sibling test with cousins?
You can order a test to know your link directly on the internet at home in order to receive the sampling material at home.
It often happens that the participants can be geographically distant, in this case the laboratories propose to send a genetic kit to each of the participants .
For the moment, it is still impossible to obtain a DNA test in a pharmacy , moreover only a laboratory with genetic analysis equipment and accredited by international standards can provide the result for a sibling test.
How to do a DNA test between siblings?
Consent is the agreement you give to the laboratory to use your DNA for the purpose of carrying out a genetic analysis. It is mandatory if you wish to take a sibling test. Consent can only be given explicitly by an adult and fully lucid person. This agreement must be drafted after having received information about the outcomes of the test, through a contract or a consent form.
It is against the law to do a DNA test without the person's consent.
For minors, consent must be provided by one of the legal parents.
What is consent?
- 5-7 days using buccal swabs, for all participants
- 10+ days if a participant uses discrete samples
This time is calculated from the moment your samples arrive at the laboratory. The delivery time is not taken into account.
What are the analysis times for a sibling test?
The price of a sibling test can vary depending on the laboratories. Generally located around three hundred euros for the participation of two participants. You can easily find a sibling test for 269€, 299€ or even 189€.
The final price of the test may also depend on the options you have chosen, such as for express results or the addition of a participant or a discrete sample.