Paternity testing can answer a lot of questions, but some of these questions are trickier to answer than others. Good examples are when DNA paternity testing involves twins, either as children or alleged parents. Identical twin fathers are by far the most difficult to detect due to their indistinguishable DNA samples; rarer cases, such as twin children with two different fathers, are much easier to solve despite their infrequent occurrence.
While reaching conclusive DNA test results when alleged fathers are identical twins is not impossible, the process is outrageously expensive and therefore cost-prohibitive for most folks. As medical advances in the field of genetic testing become more affordable and commonplace, it may become easier to answer these questions of paternity in the future. For now, those answers are fleeting.
Paternity test results with identical twins
There have been many cases in which the alleged fathers are identical twins. The DNA test results are almost always inconclusive since identical twins share almost identical sets of DNA.
Until recently, the consensus has been that identical twins share completely identical DNA, but recent studies show that isn’t necessarily true. Rather than looking at the standard 15 markers analyzed in today’s paternity tests, highly-advanced and impossibly-expensive DNA tests that analyze the entire genome sequence – as many as six billion markers – are able to identify at least a single mutation in one of the identical twins’ genetics that has been passed on to the child (Sapiro). However, DNA tests that are presently accessible to the public do not analyze enough markers to distinguish the two, presenting a serious problem in court cases to establish paternity for child support.
Hopefully, next-generation technology will be able to identify the differences between identical DNA in a way that’s affordable as well as accessible to the general public. Until then, paternity involving identical twins remains unsolvable.
Fraternal twins and different DNA test results
Unlike identical twins, it is possible for fraternal twins to have different fathers, though these cases are extremely rare.
This occurs through a process known as superfecundation, which is the fertilization of two or more eggs from separate acts of intercourse. Studies show that this is possible because the window of time in which a woman is fertile can span from five to seven days (Weller). While an egg only remains fertile for 12-48 hours, sperm can live in a woman’s body for four or five days, thereby expanding the possible time of fertilization (Wikipedia).
This process can only occur with fraternal twins. It is not possible for identical twins to have two different fathers since their identical genetics can only occur when one sperm fertilizes one egg and the resulting cell divides (Worland).
Superfecundation is assumed to happen more often with just one father; however, tests are only able to detect its occurrence when there are two different fathers. The latter group makes up for approximately 2% of paternity suits involving fraternal twins in the United States, generally drawing a lot of attention from the media due to its rarity (Worland).
Even though testing for superfecundation is rarer than administering paternity tests to identical twin fathers, it is a far easier mystery to solve. Provided the fathers in question are not identical twins themselves, modern-day DNA paternity tests can conclusively determine whether fraternal twins have different fathers.
Answering questions of paternity in cases involving fraternal twins
Court cases involving fraternal twin children with different fathers can be resolved with a legal paternity test without complications in the DNA testing process. However, you can always make sure ahead of time with an at-home paternity test from HomeDNA Paternity.
Do you have fraternal twins and suspect there may be two different fathers? Get the answers you need today with our paternity test kit. Click here to learn how it works.
How much does it cost to do a paternity test with twins?
Although you can use one HomeDNA Paternity kit to test twin children, you’re still asking two separate questions:- Is the man tested the biological father of Twin A, and
- Is the man tested the biological father of Twin B?
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Sources Sapiro, Anne. “Understanding Genetics.” Understanding Genetics. Stanford University, 5 Aug. 2014. Web. 21 July 2015.
“Superfecundation.” Wikipedia. Wikimedia Foundation, n.d. Web. 21 July 2015.
Weller, Chris. “NJ Twins Have Two Different Fathers, Court Rules.” Medical Daily. Medical Daily, 08 May 2015. Web. 21 July 2015.
Worland, Justin. “The Science of How Women Can Have Twins With 2 Different Fathers.” Time. Time, 8 May 2015. Web. 21 July 2015.
Randa j says
I know I’m not a scientist and do not know too much about scientific DNA. I do know that no two people are 100% exactly the same so they have different DNA. We may not have the ability or the science to be able to determine the difference yet. First of all, if you have two different finger prints, you are not exact. Secondly, there’s nothing in the world that is exactly 100% the same. It may be minute, but there is always a difference.
IDENTIGENE says
Hi, Randa. You’re right that no people are 100% alike. The problem with identical twins is that the genetic markers that are used as a standard for all paternity tests are likely to be exactly the same for both men. In order to determine which identical twin is the father, the two men’s entire genomes would have to be tested. This costs thousands upon thousands of dollars at this point in time, so it is cost-prohibitive for most people.
jazzy says
what if its two brothers that’s not twins but i could only test one? could the test tell if its the father or uncle??
Identigene says
Hi, Jazzy. It’s best if both brothers can test. But if one can’t, it’s absolutely essential that you let the lab know ahead of time that the other possible father is the biological brother of the man being tested. You would also want to contribute your own DNA to the test. If you have more questions, feel free to contact us at 800-344-9583.
mamab says
Which test do you buy in this scenario? Can the result come back as inconclusive with mom, baby, and only the one brother who is willing to submit DNA? Does the age of the child matter?
Thank you for this information. I’m pleased to learn there is a possible solution to such difficult situations.
HomeDNA Identigene says
The age of the child never matters for DNA testing.
Marie says
What if they are identical do I need to test both to find out the father and witch one would you recommend?
HomeDNA Identigene says
Hi, Marie. If your twins have been confirmed to be identical, you only need to test one of the children. Identical twins all come from the same biological father.
Skye says
Me and my identical twin brother slept with the same girl, he got her pregnant and i slept with her a couple months later, the thing is the mother and myself are 0 positive and my twin is A positive but the child is 0 positive, she also looks more like me rather than him is it possible for my brother to get this girl pregnant but for the child while jestating in the stumoch takin my DNA and hence being my child?
HomeDNA Identigene says
No, that’s not possible.
Katie Lee says
I am pregnant with twins. Am I able to find out the father while I am pregnant?
HomeDNA Identigene says
Hi, Katie Lee. Prenatal paternity tests are not reliable for twins. Sorry!
SHANNON says
I recently discovered a possible half sibling through ancestry dna but then discovered her dad, my potential dad is a identical twin. Can it be established which twin is my dad?
HomeDNA Identigene says
Unfortunately there’s not a way to do so, since identical twins have identical DNA.
Aaron says
I have fraternal twins and I bought the kit and wanted to test both of them instead of their mother. Can I do that?
HomeDNA Identigene says
Hi, Aaron. Yes, you can. However, keep in mind that you’ll need to pay two separate lab fees, since we’re answering two separate questions. I suggest calling us to register the kit and pay for the lab fees, since you’re using the kit differently than how it was intended. That number is 800-344-9583 (M-F, 8:30 am to 5:30 pm Eastern).
TJ says
My identical twin recently passed away and the child born to “us” is now rightfully curious as to which of us is his true father.
1. Can a conclusive test be completed with only my DNA and the child?
2. Can you emphasize in maybe approximate figures (ex. $5,000, $20,000, etc.) what you mean by a full genome test costing “thousands upon thousands of dollars”?
3. If the test can be completed using only my DNA and the child, what would be a rough estimate to have the full genome test done (I’m not going to hold your feet to the fire on a rough estimate ;) ?
Thank you for any information you may provide in hopes of putting this 33 year delema to rest.
Respectfully,
TJ
HomeDNA Identigene says
Hi, TJ. My condolences on the loss of your brother. Yours is a difficult scenario, but here’s what I suggest you do:
(1) Do a standard paternity test with the child first. This is the most cost-effective strategy. If you are “excluded,” then you know you’re not the biological father and no further testing is needed.
(2) If you are “included” in that test result, then you need to see if you or your late twin is the biological father. Are you absolutely sure you are identical twins? Sometimes twins are misidentified because doctors make that assumption if the twins share just one placenta. But sometimes twins who share one placenta are really fraternal. The only way to find that out at this point is to compare your DNA with your late twin’s, ideally with a blood card from the coroner or funeral home. The child can also be tested with the DNA from that blood card.
(3) If it turns out you are identical, a full genome sequencing costs about $1,000 per sample ($1,000 for you, and $1,000 for your late twin). Then you need to pay for the services of an analyst who is experienced in determining paternity for identical-twin cases, and those are few and far between.
I hope this helps a little, and good luck!
Beth says
Is it possible and what would I need. I have narrowed down possible BF strongly suspect one over the other. No volunteers from his sister nor his children . I do have DNA from his sisters daughters and sisters brother . Would this be enough to prove paternity ?
HomeDNA Identigene says
Hi, Beth. Those relationships are too distant for the type of testing we do. You may all want to do a test with an ancestry company that provides possibilities of more distant relationships.