Yes, twins can have different eye colors. Two types of twins can be born: fraternal twins and identical twins.
Two fraternal twin babies have 50% of the same genes. So, having two different eye colors is common for them.
However, identical twins have almost the same type of gene just like siblings. So, when think about do siblings have same blood type or not depend on the probability of ABO blood grouping, eye color has no such 50/50 probabilities.
Only one out of a million genes are different. If those different genes are involved in changing color, they may be born with different eye colors.
How can twins have different eye colors?
The reasons for twins’ having different eye colors are described below.
Because of the lower level of melanin
Melanin is a pigment of the human body that determines the color of human eyes. Genes create it. However, the gene both twins get isn’t completely the same.
Melanie Schmitt from uwhealth.org saysA. Schmitt, M., 2022. Melanie A. Schmitt, MD. [online] Uwhealth.org. Available at: <https://www.uwhealth.org/providers/melanie-a-schmitt-md> [Accessed 22 August 2022].
“One baby may get the gene from his or her dad, whereas the other one may get it from their mom. That’s why they will have different levels of melanin and be born with different eye colors”
When both have different types of genes
Twins having different types of genes is rare but not impossible. Different reasons, like radiation, defects in the past generation, or other natural reasons, can do so. Some genes like OCA2, HERC2, or SLC45A( shared in an article) can get changed into splices. That’s why both twins may be born with two different eye colors.
Because of different genetic makeup
If the twins are fraternal, they will bear the same 50% of genes in their bodies.
It means 1.5 billion base pairs out of 3 billion base pairs of genes are the same.
As a result, the genes that are directly involved in the eye colors of two twins may differ.
This case can also occur with identical twins. Identical twins don’t have many differences between them.
If you don’t know what are these two types (Fraternal & Identical twins) then let’s come to know
Only 1 out of 1 million genes aren’t the same. But those different genes can be involved in changing their color. As a result, they will have different eye colors.
When parents have different eye colors?
Parents having different eye colors is completely normal. Their eye color always determines what their children’s eye color will be.
And there can be some exceptions when their twin children are born with different eye colors.
shared a chart to clarify what type of eyes children will get when their parents have different eye colors.
The above chart notes that two blue-eyed parents can’t have a brown-eyed baby [source]Debrowski, A. (2022, June 14). The Human Eye Color Chart. All About Vision. Retrieved August 22, 2022, from https://www.allaboutvision.com/conditions/eye-color-chart.htm
Because of environmental factors
A twin may be born with the same color, but their eye color may change when they grow up. Humans’ eye color usually doesn’t change after 6 years. According to a published journal, scientists have found in a study that 10% to 15% of 1359 twins’ eye color can change after that particular age.
They also say 3.8% to 8.6% of babies’ eyes become darker or lighter after 18 years. These changes occur because of what type of environment they grow up in or what type of food they eat, etc.
Do twins with two different eye colors exist?
Yes, twins with two colored eyes exist.
Most often, identical twins have the same eye color because they have the same DNA. That’s why they share the same genes. Hence, some genes like OCA2, HERC2, or SLC45A are responsible for eye color. That’s why, in the maximum case, identical twins have the same eye color.
However, there are some exceptional incidents where identical twins have different eye colors.
Some rare events, like what type of environment they grow up in, what type of food they eat, etc., can change their DNA.
As a result, the melanin in their eyes changes. So they start growing up with two different eye colors.
Do fraternal twins have the same eye color?
Fraternal twins are born with 2 different sperm planted in 2 different eggs. That’s why they can have two different faces, looks, or eye colors. Only 50% of genes are identical to fraternal twin babies.
As a result, most of their body parts don’t look the same. However, if all the genes involved in determining eye color match the two siblings, they can have the same eye color. Both children get 50 genes from their parents’ bodies. So, it is not uncommon to have fraternal twins with the same eye color.
Can identical twins have different eye colors?
There aren’t many differences between identical twins.
Dr. Barry Starr says in an article “only one unique gene in a million is present. However, those specific genes may influence their ability to change hue” Therefore, they may have different eye colors.
Twins share the same womb for an exact time in their mother’s body and are born almost at the same hour. As a result, they often have similar appearances and behaviors. However, they may still possess some differences, which may surprise people.
1.5 billion out of 3 billion fraternal twin babies’ genes don’t match each other. As a result, you can see fraternal twins with different eye colors.
Having different eye colors for identical twins is exceptional. You usually won’t find any differences in their bodies. However, they may have different genes, which can cause their eye color to differ.