More often than not, conducting paternity tests is something surrounded by an interesting yet controversial story. The UK paternity testing facility, in particular, often receives reports about a client requesting for a paternity test due to their uncertainty about the child’s real father.

The same case also applies to biologically-related possible fathers. Usually, the likelihood of getting an error after testing biologically-related fathers increase in relation to how close the relationship is. For instance, more errors will likely occur in a test between brothers than in a test between distant cousins.

With biologically-related paternity testing, the likelihood of errors increases because their DNA would have similar strands that could be difficult to break down. Though a person would definitely have a unique DNA, with even twins carrying differences in their DNA strands, the slight differences between two closely-related people might not be easily identified.

With this said, it is best to have the paternity test conducted by experienced labs that are equipped to run extended DNA testing. These labs use more in-depth analysis that would be able to differentiate similar DNA strands. You even have the option to just have the test run on one of the biologically-related fathers and get a result even if the other party opts out of it.

Conducting a DNA Test on Brothers

Full brothers share the same gene pool that they derived from their parents. However, as with twins, two brothers would definitely not end up having exactly the same DNA mixture. There will be enough distinctions that would warrant clear differences upon testing, and it is highly unlikely that they would pass on the same genetic marker to the child.

While you may still get a result after testing just one of the brothers, it is still best to have the two take the DNA test. The likelihood of getting an error would be small under an experienced lab, but the chance is still there. Testing both potential fathers could also be used to test out other genetic markers that the two of them might share with the child.

Conducting a DNA Test on Twins

When conducting a DNA test on twins, consider first the two types of twins: identical and fraternal. DNA tests conducted on different types of twins would yield significant differences.

Fraternal Twins

Fraternal twins are twins that are born on the same day, but they don’t look alike. Fraternal twins can be considered similar to regular siblings, and the differences between their DNAs can be easier to identify in a paternity test.

In a DNA test, the DNA between two fraternal brothers would be diagnosed similar to a regular non-twin relationship. There is a significant difference in the two’s genetic structure, which means the likelihood of producing errors during the test would be lower. Like regular brothers, even though it is possible to have just one brother tested, you will still get more accurate results if both can take the paternity test. Doing this will enable the lab to fully analyze the child’s genetic markers.

If both agree to take the paternity test, remember to inform your chosen DNA testing facility or doctor that the two are fraternal twins so that they can conduct necessary additional testing procedures.

Identical Twins

Unlike fraternal twins, identical twins look almost exactly alike. This means that the two siblings share the same genetic features and a similar DNA code. Unlike other relationships, differentiating the DNA strands between two identical twin brothers is a more complicated and taxing process. Most hardware used to date, even the most advanced scientific tools, are still not able to fully differentiate two samples taken from identical twins.

When conducting a DNA test between identical twins you must be prepared to have the two take further tests. You might have to repeat the same tests over and over and hope that the scientists can discover a mismatch.

Father And Son

An offspring gets 50% of his genetics from his father and the other 50% of his genetics from his mother. In genetic math, the offspring gets an equal divide of genetics from his parents. However, this simple math often does not translate to a simple answer in the case of a paternity test conducted between a father and his son.

When the two potential fathers share a father and son relationship, it must be mentioned to the testing facility beforehand, as failing to mention this might result in a high false-positive result.

Also, similar to all cases mentioned above, your best chance of receiving an accurate result lies in both parties agreeing to take the test. But in this case, the likelihood of success further increases if the mother agrees to undergo a test as well, which will help isolate the genetics of the offspring to an easier degree.


The likelihood of getting an error or a false positive on a test conducted between two cousins is low because the chances of the cousins having matching DNA is also extremely low. In fact, a DNA paternity test done on cousins can be comparable to a DNA test done on two complete strangers. This means that the genetic connection is already too different, and the likelihood of making a mistake in the test is virtually impossible.

Final Tips

Requesting for a paternity test on two individuals as a child’s potential father can be complicated, but having these two individuals share a close biological relationship makes the process even trickier. If you find yourself in this situation, keep these tips in mind when conducting a DNA paternity test:

  • Have both potential fathers take the test if possible.

  • Speed up the process by contributing to the mother’s DNA. Aside from getting results more quickly, the likelihood of these results being accurate also increases.

  • Always remember to inform the testing facility ahead of time if the fathers in question are related. Don’t forget to specify the degree of their relationship.

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