Paternity Testing: Twins With Different Fathers

Apr 16, 2016 | Science and Technology

Paternity DNA testing for twins presents unique challenges that require attention to additional details. Before beginning the DNA testing process on twins who may have different fathers, there are several factors to consider.

There are two possible scenarios when the paternity of a set of twins is in question, depending on whether the twins are Identical or Fraternal. Because Identical Twins have exactly the same DNA, they would therefore have the same father. (If it is unknown whether the twins are fraternal or identical, a Twin Zygosity Test can determine this.)

  1. If paternity of the set of twins is in question and the twins are thought to be identical:

    A DNA paternity test can be performed by comparing the twins’ DNA to the alleged father(s). It is recommended that the mother participate in the testing, but it is not required.

DDC strongly recommends that both twins participate in the paternity test for several reasons. First, taking a DNA sample from each twin will confirm that the twins are indeed fraternal or identical, because the DNA profiles generated for the twins during the testing process can be compared. Identical twins have the same DNA because a single sperm cell has fertilized one egg, which then splits into two. On the other hand, fraternal twins may have different DNA profiles because they come from two different eggs that have been fertilized by different sperm cells.

Additionally, if the paternity test results will be used for child support or other legal benefits, government agencies often require that both twins’ names appear on the report, and this is only possible if both twins are tested.

  1. If paternity of the set of twins is in question and the twins are thought to be fraternal:

    In the case of fraternal twins, a woman has ovulated more than once in a given month, thus releasing more than one egg. If this occurs and each egg is fertilized by sperm cells from the same man, fraternal twins are formed that have the same father.

    While extremely rare, it is possible that each egg is fertilized by sperm cells from two different men, thus forming twins with two different fathers, called bi-paternal twins. According to recent studies published by the National Institutes of Health, it is estimated that approximately 1 in 12 fraternal twin sets are bi-paternal, meaning that each twin has a different father (Note that fraternal twinning is a relatively rare event in itself—fraternal twins make up about 2% of the world’s population).

Each paternity test involving fraternal twins is unique, but the following steps present possible DNA testing scenarios:

  1. Initially, it is necessary to test only the mother, alleged father(s) and both twins. This test can determine if the alleged father(s) is (are) biologically related to one twin, both twins, or neither twin. DDC recommends having all the alleged fathers participate in the initial DNA test, if possible (they can submit samples at the different appointments/times).

  2. If the initial DNA test proves that an alleged father is related to only one of the twins, this means that the twins are bi-paternal. In the case of twins with different fathers, it is possible to perform another paternity test with a second alleged father.

  3. If the initial test proves that the alleged father (s) is related to neither twin, the tested parties may choose to have another alleged father tested.

*Note: After the mother and each twin has provided a sample of their DNA through DDC’s chain of custody procedure, there is no need for them to have their cheek swabs taken repeatedly if additional testing is needed. In most cases where additional testing is required, there is enough DNA left from the original sample to perform the additional analysis, if the second test is performed within 90 days of the first test. Please call one of our paternity testing specialists now at 1-800-613-5768 to discuss your case further and for our complete Twin Paternity Testing Fee Schedule

  1. Jennifer

    I am pregnant with twins at the moment. I was intimate with two men at a party and when I found out I was pregnant by one of them. I went to my doctor to have a paternity test to find out who was the father for possible medical concerns. I was shocked to find out I that my babies both had different fathers (Bipaternal or Superfecundation) the DNA test really gave me peace of mind. Both men are brothersand have very similar facile features and they are black. I am a redhead with green eyes. Having said that I doubt that I would have known that they had different fathers when they are born if I hadn’t gotten that DNA test

    • DDC

      Thanks for chiming in, Jennifer. DNA tests are pretty incredible, and isn’t it wonderful that you were able to find out while pregnant? Superfecundation is unusual, but it happens from time to time, as you found out. For twins, however, you must have had some kind of invasive testing done. For non-invasive prenatal testing that uses just a simple blood sample from the mother and a cheek-swab DNA sample from the alleged father, testing twins is not an option. But for a single-fetus prenatal test, it’s the perfect choice. If anyone is interested in prenatal testing, you’re welcome to learn more here:

    • Cym



  2. Davonna

    I had a DNA test on my fraternal twins and the father was shown to be both twins father I don’t think he’s 1 of the twins father how likely can a DNA test be wrong with twins?

    • DDC

      Hi, Davonna. If you tested with an accredited lab, it’s not likely at all.

  3. Brennan

    I am pregnant, I don’t know how many babies yet until my ultrasound. Why don’t you do prenatal paternity tests for mothers having multiples? I understand they can have different sets of DNA, but I am not referring for testing for legal purposes. Why won’t you allow testing for twins even if it’s for the mother’s peace of mind? Is there any way to test the child’s ancestry, if not paternity?

    • DDC

      Hi, Brennan. It’s not a matter of we don’t want to test…it’s a matter of science feasibility. We cannot test multiple fetuses because there is no way to assign the fetal DNA to separate fetuses. It is also possible that fraternal twins could have different biological fathers. We have a no-multiples policy across the board: not even if the twins are identical. Ancestry testing for fetuses is also not possible.

  4. Taylor

    I have a question. I did the prenatal paternity test with DDC when I was 9 weeks pregnant. I got the results back and everything was good. I found out a few weeks later that I am carrying identical twins- di/di with two different placentas. Does that mean that my test results are invalid? I got a 0.0% on the potential father which I wanted, I spoke with my representative Nancy on the issue (she was SO helpful) she said my test results are still accurate? But there’s a no multiples policy? I really did not know it was twins until I was 14 weeks. I just really need some peace of mind because now I am afraid the test results aren’t accurate

    • DDC

      Hello, Taylor. Chances are good that your result is correct since the twins have been deemed identical. However, this test has not been validated for twins and so we cannot confirm this. You may want to do a postnatal test once the babies are born to make sure and for your own peace of mind.

      • Heather

        I have a newborn and the father is a twin. The problem is I had sex with both twin brothers in the same week. Conception date was said to be June 5th based on ultrasound. Is there a way to DNA test both twin brothers to see who is the father? Or anyway to truly know? They are identical brothers.

        • DDC

          Hi, Heather. Seeing as they are identical, there is no way to know.

  5. Diane

    I had a DNA test while I’m pregnant at the time I didn’t know I was pregnant with twins, would my results be accurate.

    • DDC

      Hi, Diane. Our test is not validated for pregnancies involving twins or other multiples.


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