Whenever someone finds out I'm an identical twin, one question is always asked.

"So, who's older?"

No matter which one of us is asked, my brother Daniel and I will always repeat the same answer we've given hundreds, if not thousands, of times before.

"Our parents never told us,” says Daniel. “We always say that, along with the fact that they read in a book that by telling us which was older, it would give the older one a superiority complex, and the younger child, an inferiority complex. So, we don't know."

Most identical twins know who was born first. In fact, as children, we were relentless in attempting to find out, but our parents refused. We asked in every way we could imagine, even pleaded with them to tell. But, the only information we were able to extract was that the time difference between us was only five minutes, and that it really didn’t matter.

After a long time, we both came to realize that our parents’ decision helped us become the separate individuals that we are today. It allowed us to step out of each other's shadow and become David and Daniel – instead of the Manly twins.

If I was to find out that I was born first, or that Daniel was a few minutes older, I do not think it would affect my life in any big way. But, to everyone else, it is always the first, and most important, question they ask.

"We’re still us after all,” says Daniel. "That doesn’t disappear. We are still the same people we always have been, regardless of who is older."

The perils of childhood

My parents were veterans of my “perfect” older sister, and thought they could handle their next child with relative ease. Suffice to say, they were mistaken.

In fact, my parents still recall the first few years with a mix of horror and surprise.

"I cannot believe we survived," says my mom with awe. "We did not know what to expect with twins, but it was much harder than we thought."

But, they did read a lot of books on how to raise twins, and while they did not help with actually raising us, they did help in other ways. These books helped our parents make some very important decisions early on that helped my brother and I become the individuals we are today, instead of simple carbon copies of the same person.

In addition to not divulging who was born first, our parents also split us into different classes in school as soon as possible. Their reasoning was that twins could easily fall into becoming the same person, and be 100 per cent dependent on one another.

One of the most important things our parents ever did, was instil into our minds that while we are twins, it should not be what defines us.

Identical does not mean the same

While most people can take solace in the fact that they are unique and one of a kind, twins do not have that. Because twin DNA is practically identical when they are born, each must take on a journey of self-discovery to forge their own identity, which is different than those who are not twins (or as they are known in the twin community, "singletons.")

Giving birth to twins is a relatively rare natural occurrence – it occurs in approximately one in every 1,000 births worldwide, according to an article published in 2003 by G. Thomas Couser. But, in industrialized nations like Canada and the United States, the birth rate of twins (or other multiple births) is over 20x that, primarily due to the large use of infertility treatments.

Dizygotic (or fraternal) twins occur when two or more eggs are released and fertilized at the same time, which is greatly aided by the use of fertility treatments. Fraternal twins shared approximately 50 per cent of their DNA with each other, like any other siblings. However, identical (or monozygotic) twins come from a single egg that splits into two separate embryos by a still not well-understood mechanism, and have almost 100 per cent the same DNA.

But, each one of the thousands of twins born worldwide each day must struggle with establishing identities that are unique from their genetic counterparts. For fraternal twins, who can even be different sexes, it is easier, as they akin to siblings who just happen to be the same age. But, for identical twins, it is that much harder.

For example, Daniel and I are known as "mirror image twins," which are approximately 25 per cent of all twins. That means some of our features are the exact opposite of one another, such as our fingerprints. Imagine you had to craft a separate identity from someone who mirrored you exactly with the same likes, dislikes, etc…

Picture left: Which is which? (Photo courtesy of David Manly)

How would you do it?

I can tell you from personal experience, that it is not easy.

Singletons do not know or appreciate how much time and effort is required for twins to step out of their previously established twin identity and create a new one all their own. In fact, making themselves an individual is one of the most difficult parts of being a twin.

The twin stereotype

A major hurdle for a twin's developing individuality is one that they will encounter from the general public – the twin stereotype.

As a twin, it is almost impossible not to run into these assumptions throughout life, such as the belief that we can read each other's thoughts, feel each other's pain, and are the exact same person. Not surprisingly, while many people believe there is some truth to these claims, they are all false.

Elise Milbradt, an identical twin, knows this all too well.

She says that being a twin creates many complex obstacles that one must endure. "There are all these stereotypes that people assume about twins, which are ridiculous and not true. But, people believe they are, which makes all the difference," she says.

"It's not just the constant confusion and the not knowing who is who – I mean, that's a part of it, but you get used to that. The worst part is that people really do believe that you are the same person."

My brother and I were, and still are, constantly confused for each other. Even our parents and friends, some who have known us for almost 27 years, still can and do confuse us from time to time.

This has led our family and friends to come up with a wide variety of ways to tell us apart, from the relatively simple to the just plain odd.

"I remember one girl in grade four," says Daniel, "who used to tell us apart by the colour of our lunch boxes! That stuff is ridiculous, since the easiest way to tell us apart is to get to know us. Once you know one twin more than the other, you start to notice the differences ... like I'm a little more reserved, while David is more outgoing. Or that David tends to talk a lot, while I usually just sit back and listen."

This constant confusion of who is who can create a rather difficult environment for individuality to develop, which has led to many scientific studies on the subject.

The science of identity

One study by Barbara Prainsack and Tim Spector in 2006 stated that, despite the strong bond between twins, the preconceptions of non-twins in their lives could potentially create a drive to seek out and claim a unique identity from that of their twin.


"[The fact that twins] are affected by the failure of some singletons to fully acknowledge the individuality of human beings who look very much alike and/or go through large parts of their lives together, indicates that this is much rather a problem related to superficial characteristics of similarity (such as wearing similar clothes, having the same eye and hair color, etc.) than to identical genes."

To overcome this problem, many parents of twins will attempt to manufacture some sort of a difference by dressing their children in a set colour scheme – for example, I was always in blue and Daniel in red.

Image right: Me (left) and my twin brother Daniel (right), as kids. (Photo courtesy of David Manly)

And it's not just us. Many parents choose separate colour schemes for their twins.

For example, identical twin girls Amy and Jaclyn Jacobs were always dressed in yellow and pink, respectively.

According to Jaclyn, wearing those separate colours may have influenced her identity more than she thought.

"It never occurred to me, but if you directly compare me and Amy, I'm the one who is more interested in fashion and girly things, while she doesn't really care about that stuff. Wearing pink all those years may have helped with that."

While many parents dress twins in similar clothes when they are babies and young children, that trend does not usually continue as they age. According to a study released in the UK in 2005, doing so could result in the development of stigma and isolation from their peers.

Kate Bacon, who authored the study, explored the dynamics of twinship with respect to their family environments and the development of their individual identities. She noted that one of the only ways for twins to be recognized as different is to work together to eliminate as much personality overlap as possible.

"Whilst parents may ‘set the stage’ for twins’ presentations of self, twins actively engage in the business of ‘identity work’ and utilize each other to try to manage other people’s perceptions of them, to avoid social stigma and to bring off a convincing performance of who they are."

Bacon is referring to the strong bond that twins develop for one another, and that in some cases without each other, they cannot truly express themselves. While I do not agree with all of her conclusions, I have noticed that I do not have to hide who I am to my brother.

This is because, as twins, we have spent much of our lives together, and know each other very well. Jaclyn Jacobs says that this bond is closer than a friend, a sibling, or even a significant other.

Image left: Amy (left) and Jaclyn (right) Jacobs. (Photo courtesy of Jessica Salamon).

Her sister Amy agrees.

"Singletons cannot understand the bond between twins," she says. "It's like having someone around who understands the way you work."

My brother smiled when I told him this.

"It's true," he says. "We just get each other."

"It's not telepathy or some sort of psychic connection – we've just been raised together, had similar experiences, and share many of the same likes and dislikes. Our brains just work in a similar way."

And yet, all the twins I spoke to, including my brother, agreed – that there comes a time where being tethered to someone close to you is no longer needed.

"There came a point where I needed, really needed people to know me for me," says Elise Milbradt. "I wanted them to know me as Elise, the person who happened to be a twin, not the twin who happened to be named Elise."

"After all, you don't want to be twins forever."

And that is the real secret about twins. While we are twins, it is not the only thing that we want to be known for.

After all, everyone is an individual – even a twin.

About the Author: David Manly is a Canadian freelance science journalist who holds degrees in Biology and Zoology, as well as a Masters of Journalism. Having worked in a lab, he now spends time writing about the wondrous world of animals for Lab Spaces, as well as for his own blog The Definitive Host, and you can always find him on Twitter (@davidmanly). He and his twin brother Daniel (who is a teacher in Canada) are very close, but still individuals. That said, since they are identical twins, they still do enjoy getting confused for one another from time to time.

The views expressed are those of the author and are not necessarily those of Scientific American.