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How to do a DNA test between siblings?

Updated: Mar 26


Genetic research today allows for resolving doubts of siblinghood that may exist between brothers and sisters, and thus determining the biological parentage link on both the paternal and maternal sides. It makes sense in this regard for this DNA test to be conducted by comparing the genetic profiles of one or more members of the sibling group to determine if a biological link exists.





Know that there are several DNA paternity tests available to address doubts about sibling relationships, but it will always be very challenging to determine a relationship between a brother and a sister if the doubt about parentage involves members of the same family.


The choice of your DNA test will depend on your family situation but also on the available participants. Some genetic analyses may offer more accurate results based on these factors. However, please be aware that testing your genetic fingerprint is not a miraculous solution, and depending on your inherited genes, the DNA test may not answer your question about the relationship.


How to do a DNA test between siblings?


There are 3 possible analyses based on the situation that can be performed with only a genetic sample from presumed brothers.


Y Chromosome Test:

If you are seeking a paternal relationship only, meaning to know if you and your brother share the same biological father, it is advisable to take a Y chromosome test.


The Y chromosome test is a genetic comparison that determines if two male individuals share the same Y chromosomes, indicating they are from the same paternal lineage. Since the Y chromosome is passed from father to son in an identical manner from generation to generation, the deduction from this analysis will precisely confirm the paternity link between the two brothers.


The Y chromosome test will not work if the doubt about paternity is between two men from the same family.



Mitochondrial DNA Test:

If you are seeking a maternal relationship only, meaning to know if you and your sister share the same biological mother, it is advisable to take a mitochondrial DNA test.


The mitochondrial DNA test is a genetic comparison that determines if two individuals share the same mitochondrial DNA, indicating they are from the same maternal lineage. Since this DNA is transmitted from the mother to all her children in an identical manner from generation to generation, the deduction from this analysis will precisely confirm the maternal link between the two sisters.


The mitochondrial DNA test will not work if the doubt about maternity is between two women from the same family.

Sibling Test:

If you are seeking a relationship concerning both of your parents, meaning to know if you and your sister share the same biological father and mother, it is advisable to take a fraternity test.

The fraternity test is a complex genetic comparison that determines a sibling relationship between two individuals. This analysis is based on statistics and probabilities related to your genes and the laboratory's knowledge of genetic transmission. The reliability of the result of a fraternity test will depend on your genetic heritage and the number of participants. The result will be only a percentage of the relationship.


How to do a DNA test between sisters?


There are 3 possible analyses based on the situation that can be performed with only a genetic sample from presumed sisters.


X Chromosome Test:

If you are seeking a paternal relationship only, meaning to know if you and your sister share the same biological father, it is advisable to take an X chromosome test.


The X chromosome test is a genetic comparison that determines if two female individuals share the same X chromosomes, indicating they are from the same paternal lineage. Since the X chromosome is transmitted from father to daughters in an identical manner, the deduction from this analysis will precisely confirm the paternity link between the two sisters.


The X chromosome test will not work if the doubt about paternity is between two men from the same biological mother.


Mitochondrial DNA Test:

If you are seeking a maternal relationship only, meaning to know if you and your sister share the same biological mother, it is advisable to take a mitochondrial DNA test.


The mitochondrial DNA test is a genetic comparison that determines if two individuals share the same mitochondrial DNA, indicating they are from the same maternal lineage. Since this DNA is transmitted from the mother to all her children in an identical manner from generation to generation, the deduction from this analysis will precisely confirm the maternal link between the two sisters.


The mitochondrial DNA test will not work if the doubt about maternity is between two women from the same family.


Sibling Test :

If you are seeking a relationship concerning both of your parents, meaning to know if you and your sister share the same biological father and mother, it is advisable to take a fraternity test.


The fraternity test is a complex genetic comparison that determines a sibling relationship between two individuals. This analysis is based on statistics and probabilities related to your genes and the laboratory's knowledge of genetic transmission. The reliability of the result of a fraternity test will depend on your genetic heritage and the number of participants. The result will be only a percentage of the relationship.


How to do a DNA test between brothers and sisters?


There are 2 possible analyses based on the situation that can be performed with only a genetic sample from presumed brothers and sisters.


Sibling Test:

If you are seeking a relationship concerning your father, your mother, or both parents, meaning to know if brothers and sisters share the same biological father and mother, it is advisable to take a fraternity test.


The sibling test is a complex genetic comparison that determines a sibling relationship between two individuals. This analysis is based on statistics and probabilities related to your genes and the laboratory's knowledge of genetic transmission. The reliability of the result of a fraternity test will depend on your genetic heritage and the number of participants. The result will be only a percentage of the relationship.


To improve the reliability of this result, it is recommended to provide as much genetic material as possible to refine the research and thus have a more precise result.


For this, you can:


Add the DNA of the available parent (e.g., biological mother).

Add brothers and sisters from the sibling group.


Mitochondrial DNA Test:

If you are seeking a maternal relationship only, meaning to know if a brother and a sister share the same biological mother, it is advisable to take a mitochondrial DNA test.


The mitochondrial DNA test is a genetic comparison that determines if two individuals share the same mitochondrial DNA, indicating they are from the same maternal lineage. Since this DNA is transmitted from the mother to all her children in an identical manner from generation to generation, the deduction from this analysis will precisely confirm the maternal link between the two siblings.


The mitochondrial DNA test will not work if the doubt about maternity is between two women from the same family.




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