Twin sisters who each married identical twin brothers left Instagram users baffled after announcing that their sons are ‘brothers, cousins, and twins’.
Brittany and Briana are identical twins from Virginia, US, who married identical twins Josh and Jeremy Salyers.
The women live with their husbands and their sons, Jax and Jett, in one house and are now raising their families together.
When announcing their pregnancies, the women uploaded a post to Instagram saying: “Our children will not only be cousins but full genetic siblings and quaternary multiples!”
Although their post left many confused, other users stepped in to confirm that their statement was true, due to the way identical twins share DNA.
One person said: “Their mothers and fathers are identical twins. Both sets of parents then had kids. Same exact DNA created both.”
The science behind twins
As an accredited DNA testing laboratory, we are often asked about the science behind DNA, especially when we’re talking about twins.
While highly unusual, Brittany and Briana’s statement is correct based on the way identical twins share DNA, and how genetic profiles are passed down from the parents.
Every person inherits half of their genetic profile from each of their biological parents.
It’s this fact that makes it possible to determine who a child’s biological parents are through DNA testing (maternity or paternity testing), by analysing the DNA of a child and comparing it to that of the parents to identify matching DNA markers (alleles).
As Brittany and Briana are identical twins, each will share the exact same DNA profile. The same is true for Josh and Jeremy.
This means that genetically speaking Jax and Jett have the same parents, due to each mother and father having passed down the same DNA profiles, respectively.
While both Jax and Jett would be recognised by the law as first cousins, a DNA test would show that they are genetic siblings with both expected to have the same DNA profiles when compared with one another.
When a pair of identical twins marry identical twins, this is known as a quaternary marriage. So, the children could also be classed as ‘quaternary twins.’
How can we tell whether twins are identical or non-identical?
A DNA test such as the Twin DNA Test (Zygosity Test) from AlphaBiolabs, makes it possible to verify whether twins are identical or non-identical.
With twin testing, we can say whether multiple children from the same birth – twins, triplets, quadruplets, etc – are genetically identical or not, by analysing and comparing each child’s DNA markers.
Identical twins are known as monozygotic. This means that they were formed from a single fertilised egg that went on to split into separate embryos.
Twins that came from a single fertilised egg will have the same DNA profile.
It is sometimes unclear during pregnancy whether multiple siblings are identical. This is because identical twins won’t always share the same placenta and sac; it all depends on when the egg splits during conception.
Non-identical twins are dizygotic. This means that two eggs were fertilised by two separate sperm in the same pregnancy. Siblings that are different genders are non-identical (dizygotic).
Where can I buy a twin DNA test?
For just €139, you can find out whether your twins are identical or non-identical with a Twin DNA Test (Zygosity Test) from AlphaBiolabs.
With just a simple cheek swab required for DNA collection, we’ll analyse up to 42 DNA markers for accurate results. Once your samples have been received by our laboratory, we’ll email your secure, password-protected results either the same working day or the next working day (depending on your order).
This type of test also makes a unique gift idea for multiple birth parents or their children, with the option to test up to five siblings in the same test (additional charges apply). Simply select how many siblings you want to test when placing your order.
For more information, call our friendly Customer Services team on 01 402 9466 or email firstname.lastname@example.org.