Journey Genetic Testing is a leader in direct to consumer paternity, sibling, grandparent, and identical twin DNA testing. 855-362-5224

Twin Zygosity DNA Test – Accurate & Affordable


Are They Identical Twins or Fraternal Twins?

Our Twin Zygosity DNA Test Includes two siblings suspected of being Identical Twins, one DNA collection kit and results in ONE business day. Payment Plan Available.

Most people assume that being a twin means having a similar physical appearance. However twin type is determined long before the twins are born. The terms identical and fraternal are common words that refer to “zygosity.”

What is “Zygosity”?

Zygosity is the characteristics of the cell union that happen at conception.

Monozygotic, which means “one zygote,” refers to Identical Twins. Twins form when a single fertilized egg splits into two genetically identical parts. The twins share the same DNA set, and therefore they usually share many similar features and attributes. However, since physical appearance is  also influenced by environmental factors and not just genetics, identical twins can actually look very different. Identical twins are always same-sex sets. Dizygotic means “two zygotes” and refers to twins who are Fraternal. Twins develop when two separate eggs are fertilized and implant in the uterus. The genetic connection is no more or less the same as siblings born at separate times. They sometimes look alike, or they may not look similar at all.

Identical vs Fraternal Triplets

Identical triplets are born as a result of  a monozygotic pregnancy where there are three fetuses from one egg. Triplets that include identical (monozygotic siblings in addition to a fraternal sibling are the result of a dizygotic pregnancy. This is where one zygote divides into two fetuses and the other doesn’t.

How can I tell if my twins are “Identical” or “Fraternal”?

This is the most common question among parents of multiples. As the birth rate of twin has risen 79% over the last three decades, and continues to increase, this will continue to be a question that requires answers. Since appearance isn’t a reliable guide in determining twin type, how can parents confirm their twins’ zygosity? In some cases, it will be evident during pregnancy. Some identical twins form in a single sac, sharing a single placenta and amniotic membranes. However, the number of placentas isn’t always a clear indicator either. Two placentas of fraternal twins can fuse together and appear to be one. And identical twins may develop with completely separate placentas and sacs. The only way to know for sure is through genetic testing.

Our Twin DNA Test is a simple procedure performed sometime after the babies are born.  Some parents choose to start testing right away, while others prefer to wait to initiate testing until the twins’ features emerge later in life. The test consists of a painless buccal cheek swab collected from each twin, and then  sent to our lab where the DNA from the samples is extracted, analyzed, and compared.

Our Twin Zygosity DNA Test is 100% Accurate

The testing compares 21 specific genetic markers for each twin testing. Based on the genetic profiles for the DNA samples submitted, we can provide a final report that is 100% accurate in showing if the twins are monozygotic (identical) or dizygotic (fraternal). We are able to provide this report, in almost every case, in just one business day from when the lab receives the DNA samples.

FAQ’s About Our Twin Zygosity DNA Test

Loader image

Identical twins occur when a single fertilized egg splits after conception into two identical halves, each of which develops separately. Identical twins will have exactly the same DNA, which can be established through DNA testing. Identical twins are of the same sex and have the same eye and hair color, as well as blood type.

Fraternal twins, also called di-zygostic twins, are formed from two eggs, fertilized separately. Fraternal twins can be the same sex or opposite sexes. Their physical characteristics usually differ and their DNA always differs.

Approximately 30 out of every 1,000 births in the United States produce twins. One of every three sets of twins is identical.

Yes. In rare instances, fraternal twins can actually be half-siblings, with different fathers, even though they are born at the same time. Although the standard Journey Genetic Testing DNA twin test does not include the establishment of paternity, it is possible to determine the paternity of twins by testing their alleged father(s) or possibly by conducting a sibling (full or half) analysis on the DNA data generated from non-identical twins.

Zygosity testing works on multiples of any age, newborns to adults. The simple and non-invasive swabbing procedure allows for the rapid and painless collection of a DNA sample.

he answer to this question may be somewhat surprising. In DNA testing, a cheek swab is preferable to a blood test. The reason is that blood chimerism has been shown to exist between twins and the mother. What this means is blood stem cells can co-mingle between twins and the maternal circulation during development. This can cause some populations of blood cells to have an origin that is different from the person in which descendants of those cells are now circulating. For this reason, it is preferable to look at body tissues such as from the inside of the cheek which are not typically affected by this sort of chimerism.

Almost 33% percent of the time when there are two sets of membranes (i.e. dichorionic) identified at delivery, the twins are actually identical and not fraternal. If the fertilized egg splits prior to 2 days after conception, two complete placentas and two sets of membranes are formed causing dichorionic placentation. This is a common misunderstanding that leads to incorrect zygosity classification. This is true regardless if the dichorionic placenta is fused or not. Unless a DNA test is performed, it is difficult to definitively determine if like-sexed dichorionic twins are fraternal.

Twin DNA Test Sample Collection

The most accurate method to obtain a twin zygosity DNA sample is to use a buccal swab, which is very similar to a “Q-tip” cotton swab, The swabs are rubbed on the inside cheeks of the mouth for about 15 – 30 seconds per side. It is painless and quick. If you are not able to collect a buccal sample voluntarily we can do the testing in a more discreet manner. In these cases we are often able to test alternative samples for, at a slight additional cost. To learn more about alternative DNA samples, please CLICK HERE.

For discreet, private twin DNA testing, you do not have to obtain consent for testing for the DNA samples being submitted.  The results are only provided to the person who orders the test, unless specific written instructions to release the test results to other individuals is provided to us.

What if those testing live in different places?

We can send DNA collection kits to multiple addresses. When ordering, select how many kits you need (one per address is recommended if you cannot get together to do your DNA collection). You will be able to list the names and addresses to send the kits to on the order form. They are each coded with the same case number to be matched in the lab. Each additional kit will be sent USPS Priority mail and include all collection materials and a prepaid return label (USA addresses only).

Your DNA collection kit will have detailed step-by-step instructions on how to collect your swab sample. You can also read more about how to take a home DNA test by going to How To Collect A DNA Sample At Home.

How Much Does A Twin DNA Test Cost?

The cost listed below include USPS Priority shipping of your test kit (usually arriving in 2-3 business days), all DNA collection materials, a prepaid overnight return FedEx label (USA addresses only), all lab processing results, and an email copy of the results reviewed and signed by a lab Ph.D. International orders are shipped USPS First Class International. There are no additional surprises or hidden costs for testing. We now offer no-interest payment plans through our corporate partnership with Sezzle.

CostNumber of Siblings TestingProcessing Time
$109Twins1 Business Day
$190Triplets1 Business Day
$265Quadruplets1 Business Day
+$100Non-standard DNA Sample (per sample)+5 Business Days

An Example of Twin Zygosity Results

The Twin DNA Test results we deliver are for the purpose of determining zygosity only. In almost every case we are able to deliver the results in just one business day from when the lab receives the DNA samples. Opposite-sex twins are always di-zygosity (DZ), however the zygosity of same-sex twins may be difficult to determine. The only way to be sure is by doing DNA zygosity testing. A twin zygosity test will demonstrate if two individuals are identical twins or excluded from being identical twins.

Twin Zygosity DNA Test Report from Journey Genetic Testing. Low Cost and 100% Accurate
This example shows that the siblings tested are NOT “identical” twins.

To be an identical twin, the sibling must match on every single genetic marker tested. If even one of the markers is different then the two siblings cannot be identical twins. Markers are well-studied sequences of DNA. Our laboratory can analyze specific genetic markers that represent individual regions of DNA that may differ in fraternal twins. These areas are carefully selected, because all humans share 99.5% of the same DNA.

This is expressed as a  monozygotic index (MZ). The results are either a 99.99+% included (the highest mathematically possible, or a 0% probability which means they are excluded from the tested relationship.

How we determine the results

The laboratory process used to determine zygosity are very similar to those used in forensic DNA testing and in a paternity test. The DNA locations that are analyzed are not related to any specific physical trait such as hair color, height, or personality. Twin zygosity results are are not tested at locations that might indicate whether a pe is at risk for a genetic disease.

STR (short tandem repeat) DNA processing requires the self declaration of race/ethnicity of the twins. If a legal zygosity test  is necessary, the results will look the same, except the sample will need to be collected chain-of-custody paper work. All legal testing meets AABB requirements. A legal twin zygosity test is usually only needed in the event that proof is necessary of the relationship for medical reasons, or if the twins were separated and legal identification is necessary.

Twin Zygosity DNA Test Client Reviews


Rated 5 out of 5
August 1, 2021

Got my results in 1 day! Highly recommend.


Not what I expected

Rated 4 out of 5
May 6, 2021

It was something my brother and I really wanted to know, unfortunately we aren’t identical even though we look it! Journey Genetic Testing gave us a good service, a bit expensive looking back.


Response from Journey Genetic Testing

We thank you for the opportunity to help you learn the truth through our DNA testing services. We can never guarantee a specific result, only one that is 100% accurate. We always try to provide the best service and testing at the lowest cost. We wish you the best on your journey in life!

Identical twins confirmed

Rated 5 out of 5
April 8, 2021

The speed of service was amazing. Ordered test on a Thursday afternoon and had our results in Wednesday afternoon. The kit was easy to use. I’m glad I now know I have identical twin boys! Highly recommend!


At least I know the truth

Rated 5 out of 5
March 19, 2021

My sister and I have wanted to know the answer to this question for 10 years. Sadly we are not identical as we hoped, we fraternal instead – that is ok, we still love each other 🙂 🙂


To see more of our customer reviews, please CLICK HERE

error: Content is protected !!