Our twin zygosity dna test will tell if two twins are identical or fraternal. Results in 1 business day. 100% accurate. Journey Genetic Testing is the leading provider of twin DNA testing.

Twin Zygosity Test 

Twin Zygosity Test - Results in ONE day


Identical Twins or Fraternal Twins?

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 percent 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.

A Journey Genetic Testing Zygosity 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 Test is 100% Accurate

The testing compares 24 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 mono-zygostic (identical) or di-zygostic (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.

Twin Zygosity DNA Testing FAQ's

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 Zygosity DNA 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 collecting a buccal sample voluntarily, or if you wish to have DNA twin zygosity testing to be done in a more discreet manner, we are often able to test alternative samples, 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.

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. There are no additional surprises or hidden costs for testing.

Cost Number of People Testing Processing Time
$109 Twins 1 Business Day
$184 Triplets 1 Business Day
$259 Quadruplets 1 Business Day
+$125 Non-standard DNA Sample (per sample) +5 Business Days

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.

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  monozygostic 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.

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 pehttps://dnaexaminers.com/paternity-test/rson 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 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

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

Do you offer your tests outside of the USA?

This is one the most often asked questions we get. The answer is YES.

Legal testing collections can be coordinated in over 100 countries. Please contact us at 1-855-362-5224 to learn more information about this option. Private DNA testing is the most common type of test ordered , and so we want you to know all of your options prior to ordering your DNA test.

First, we can ship a DNA collection kit almost anywhere in the world. The only exception to that is if the country you live in, or want to have DNA testing done in, does not allow shipments from the U.S.A. or DNA testing for it's citizens. The responsibility to know the rules of your country belongs to you.

Second, we have several ways to help you get your DNA samples to us. All of our shipments are sent through USPS (United States Postal Service. You can choose to either have the kit(s) send via USPS International Priority, or USPS International First Class. We are charged extra by the postal service for sending material outside the U.S.A,, and just pass that expense onto you. You can choose either way to have the kit shipped depending on your budget and need. International Priority may take 6-10 days and International First Class may take 10=16 days, depending on the country.

We provide you a tracking number for your shipment(s) so you know where it is at at all times. Once it leaves the U.S.A. and is sent to your county, there are some things that are outside of our control that may delay delivery. Among those are holds at Customs, an address that you have provided on your order form that is incorrect, or delays due to the worldwide pandemic. Our lab remains open and testing, but we just want you to understand what may delay your kit (hopefully not!).

There is an option that we are Journey Genetic Testing highly recommend for those clients outside of the U.S.A. We offer a Make Your Own Kit option, that is just as accurate to collect DNA sample with, and it saves the cost of international shipping, as well as time. There is no extra cost for this, and you select it when you place your DNA test order. If you are interested you can learn more by CLICKING HERE.

We will of course notify you by email once all the DNA samples arrive at the lab, We do recommend that whatever carrier your choose to return your DNA samples to the lab, that you obtain a tracking number for that carrier to make certain they arrive.

Our reports can be issued either in English or Spanish. If you need a report in Spanish we will need to know that at the time of your order.

We are excited to help you get the answers you need and deserve on your journey to truth through DNA testing!

error: Content is protected !!