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When it comes to UK paternity testing, it is not unusual for a customer to tell us there are two possible fathers that need to be tested for paternity and that those two fathers are biologically related. Not all biological relationships cause issues with testing or affect the likelihood of providing false results, but testing two very closely related alleged fathers requires additional care.
Although two possible fathers who are related don’t have exactly the same DNA (unless they’re identical twins), they can share so much DNA that getting conclusive results for a paternity test may be problematic. Although it is a challenge, it is definitely possible for an experienced lab to run extended DNA testing with more in-depth analysis and obtain conclusive results, even if only one of the alleged fathers is available for or agrees to test. Here are some relationship possibilities and how they may affect test results.
Paternity Testing if Alleged Fathers are Brothers
Although they are closely related, full brothers each have DNA profiles that are actually still quite distinct from one another. Some of their DNA is the same, but certainly not all of it. For that very reason, the chances of two brothers who are not identical twins matching a child at each genetic marker for paternity testing would be highly unlikely.
But because the biological relationship between possible fathers is so close, we would still recommend that both fathers’ DNA be tested against the DNA of the child in question. At the very least, it is essential to let the lab know there are two possible fathers and that they are brothers. The lab can then test more genetic markers, if necessary. It’s also important to include the mother’s DNA in testing if at all possible.
Paternity Testing if Alleged Fathers are Twins
Identical Twins
For identical twins, their DNA is as you would expect: exactly the same. Even with the most advanced technology available today, it would still be impossible in any practical or affordable way to genetically differentiate between the two fathers for paternity purposes.
Fraternal Twins
If the men are fraternal (not identical) twins, the DNA that they share would be the same amount as it would be for non-twin siblings. As with a non-twin brothers’ test, it would be preferable if both brothers could be tested, and wherever possible the child’s mother should also provide a sample. And again, the lab should be advised that the relationship exists so that additional testing is undertaken and a definitive result can be provided.
Paternity Testing if Alleged Fathers are Father and Son
50% of the son’s DNA comes from his father, so if these two men are the possible fathers of a child, there is a high possibility of obtaining a “false positive” result if only one of the men participates in testing. A good UK paternity testing lab would recommend that both men test, if possible. If that isn’t possible, conclusive results can still be obtained if the mother also agrees to contribute her DNA. Additionally, the lab must be notified before testing begins that there is another alleged father with a filial connection. This is an absolutely essential step, because the lab can then test additional genetic markers, if necessary.
Paternity Testing: If Alleged Fathers are Cousins
Even men who are first cousins don’t share enough genetic material in common to cause a “false positive” for UK paternity testing: the genetic connection is just too far removed to affect a test one way or the other.
In Conclusion
If the alleged fathers are closely-related, there are two things to remember when doing UK paternity testing:
- Test both fathers, if at all possible. If only one can be tested, then the mother should contribute her DNA as well in order to strengthen results.
- If only one alleged father can test, let the lab know ahead of time that there is a different man who could also be the father and what the biological relationship is between the two men.
If you need additional information about a DNA test or want to order, contact our experienced customer-service team on 0800 009 2969.
If alleged fathers are father and son. And one of them had a postive test result with the baby. And mother’s dna is also included. Is he the father for the child?
Hi, James. Most likely, but not absolutely. Whenever two possible fathers share a 1st degree relationship like this, it’s essential to let the lab know ahead of time so that they can take this information into account when performing the analysis. They may want to test additional markers, for example, to confirm the paternity determination. In a paternity test report, the probability of paternity given as compared to an untested, unrelated, random male of the same racial background as the man tested.
Hiya recently done a dna only included one o the two brothers who could possibly be the father. In the report back it says relatives to be excluded what exactly does this mean.
& if it comes back 15% paternity possibility does this mean that you rule out both of the brothers
Hi, Khloe. Something isn’t right with what you’re asking. A laboratory would not give out a paternity result between a possible father and child with a probability of relationship of 15%. It’s either 99% or higher, or 0% probability of paternity. Can you please explain further? Or you’re welcome to reach out to us directly and one of our experts will be happy to clarify directly: 020 3301 7346. Sometimes it’s easier to talk it through instead of writing.
Hi there I have been told that my real father isn’t my father but my cousin could be my real father how more percentage will it prove if my real father isn’t my father
Hi, Olivia. If you were to do a paternity test with your cousin and you get an inclusion results of 99.9% or higher, than you can assume your father isn’t really your father.
Hi my partner got tested with his three children
The youngest child he knows is his came back with great then 1,000,000,000,00
It’s his twin there’s a possibility that his brother is the father there’s we’re 22,000,000,00 and 35,000,000,00
Now would he do better getting re tested as there’s are lower then his youngest as it’s a paternity test especially as it’s a higher chance his brother is the father
Hi, Hayley. It is extremely important to let the lab know prior to testing that one of the other possible fathers is the biological brother to the man being tested. That way, the analysts can take this information into account when performing their calculations. Especially since the results were inclusions, the tests should be conducted again. Ideally, both men would test. If that’s not possible, then the lab must be told, as I previously mentioned.
I had a dna which came back 99% that the child was mine but recently found out that my father had intercourse with the mother around the same time aswel so could he actually be my brother instead of son??
Hi, Scott. Yes, there is a possibility of false positives in these types of cases. It would be advisable to test again…ideally, both you and your father would. If not, then just you can test and the mother of the child, but it’s absolutely imperative that you let the lab know ahead of time of the close biological relationship between you and the other possible father.
If father and son are both potential fathers then wpuld it come back positve match to either one that does swab
Hello, Lauran. No, they only share 50% of their DNA. However, there is always a small possibility that they might share the same DNA data that is analyzed for a paternity test. So if both father and son cannot test, the laboratory needs to be informed ahead of time that the other possible father is a close biological relation to the man being tested. That way, the lab can take this information into account when doing their analysis and test additional genetic markers if necessary.
hi here my husband has had a dna test recently
as it took a long time getting a result sent out i gave them a call
ive been told that further investigating is needed and that they are awaithing a reply from the mother about a posibility about relations with brother or father
my husband does not have a brother and his father is now deceased
what does this mean?
Hello, Kim. Without more information I cannot answer accurately. I suggest your husband call the laboratory and ask questions.
My father (71) has recently told my younger sister (45) years old that her father is in fact his brother. My father doesn’t speak to his brother and our parents have been divorced for 20 years. My dad speaks very nasty about my mother. This news has hit my sister hard, my father was very cold and can not understand why she is hurting so much. My sister doesn’t want to confront my mother or uncle. Are there any tests we can do between the three of us to establish if he is her father and we are true siblings?
Hello, Sharron. This is difficult, since the other possible father is a close relation to the man whom your sister has assumed is her biological father. Is your father willing to do a paternity test with your sister? If so, then you MUST tell the laboratory ahead of time of the possibility that his brother could be the father. That way, the lab can perform additional testing. I suggest you contact us to discuss possibilities further with one of our experts: 0800 009 2969
Grandma had a possible affair with her brother in law. My mom and aunt want to find out who is their real father but both these men have passed away, only grandma is alive. Is this even possible to do?
Hello, Vicky. Please contact our experts for a consultation to see if a sibling vs. half-sibling test is possible for this unique situation: 0800 009 2969
Hey I had fraternal twins
One child came back 99.99
The other one came back
99.97 what does that mean ?
Hi, Willie. Congrats on your little ones! In practical terms, the difference in data means absolutely nothing. The result is just as conclusive at 99.99% probability of paternity as it is at 99.97%. Since your twins are fraternal, they share the same amount of DNA as regular siblings (50%) and so there are bound to be differences in the strength of the data at certain genetic locations and those account for the teeny-tiny difference.