If you believe that identical twins can have different eye colors, then you are correct. But do you know how this happens?
Can identical twins have different eye colors?
Although it is rare, it is possible for identical twins to have different eye colors. Most twins have brown eyes, but any typical eye color is possible. Not only can twins have differing eye colors from each other, but sometimes one twin can have two different colored eyes.
Identical twins often cause us to look twice, no pun intended. When we see two people who look exactly alike, we tend to play the game “spot the difference.” We quickly glance at one twin, and then the other while trying to figure out how to tell them apart. But are we truly seeing double?
Eye Color in Identical Twins
When a zygote divides into two, the result is two babies who are almost identical. Identical twins share many things but not everything. They have unique fingerprints, personalities, and sometimes their own eye color.
Why Most Identical Twins Have the Same Eye Color
Most identical twins do have the same eye color because of the large amount of DNA shared by them. This is why they are referred to as identical twins as opposed to fraternal twins.
Rare Cases of Identical Twins With Different Eye Color
As you have probably experienced for yourself, identical twins usually look very much alike. Having identical twins with different colored eyes is uncommon, but it does happen. A quick Google search will yield a plethora of photos of identical twins who do not share the same eye color, skin color, and more.
Megan and Morgan Boyd are well- known twins because of their eyes. Megan’s eyes are both blue. Morgan has a condition known as Heterochromia which results in her having eyes of two colors. One eye is brown while the other is blue.
Are Identical Twins Born With Blue Eyes?
Are identical twins really identical? As we have learned, the answer is no. Likewise, not all twins are born with blue eyes. Twins can be born with blue, grey, hazel, green, or brown eyes just like any single-birth baby.
Baby Eye Color Changes
All babies, not just twins, might end up with a different eye color at age 6 months, or later, than what they started out with at birth. Most of the time, it is because a child’s eyes are turning darker as the melanocytes secrete melanin in response to light.
It is more common for a baby’s eyes to turn darker over time than to become lighter. My first child was born with blue eyes. By the time he was 6 months old, they were gray. His eyes turned brown before his first birthday.
Are Identical Twins 100% the Same?
Perhaps we should correct our vocabulary. The word identical means being the same. When we discuss identical twins, what we are really talking about are monozygotic twins. They share about 99.9% of the same DNA, which means that 0.1% is going to be different from their counterpart.
This shows up in things we can see, such as eye color or height, and it shows up in things that we cannot see, such as personality traits like assertiveness or empathy.
Is Eye Color Genetic?
Eye color, hair color, and skin color are all based on the genes passed down to us from our parents. Years ago, there were a few popular charts used in schools to teach how children could be born with brown, green, or blue eyes. This chart (source) has proven to be oversimplified and incorrect.
Today, we understand that there are at least 8 genes involved in determining eye color, and even then, mutations happen. It is believed that blue eyes resulted from a genetic mutation approximately 6,000 years ago.
What Determines Eye Color?
The color of a person’s iris is determined by how much melanin they have and where it is in the eye. Generally, the more melanin that a person has, the darker the eye will be.
If one twin is formed with less melanin, then they could be born with lighter eyes than their sibling. The “why is the sky blue” question can also be compared to the “why are some eyes blue” question.
Blue eyes look blue because of the lack of melanin on the first layer of the iris. Light enters the eye, reflects off the back of the eye, is scattered back out the front of the eye, and looks blue.
This is very similar to how the sky looks blue. Blue light travels in shorter waves and is scattered more, so this is what we usually see.
Can Triplets Have Different Eye Colors?
If twins are considered double trouble, then the possibilities of what can happen with triplets is exponential. With three babies, there is an even greater chance that at least one baby will have different colored eyes.
Can Fraternal Twins Have Different Eye Colors?
There are differences between fraternal twins and identical twins. The main difference is that fraternal twins started off as separate zygotes. Fraternal twins can look similar, or they can look nothing alike.
Fraternal twins share approximately 50% of their DNA. So just as any sibling might have different colored eyes, so can fraternal twins.
Identical twins are rare: about 1 in 300 births worldwide. It is even less common to see twins with different colored eyes. After reading this article, you will never look at twins the same again, pun intended.
Mom of three (including identical twin boys), wife, and owner of Parents Wonder. This is my place to share my journey as a mother and the helpful insights I learn along the way.