My relationship with my identical twin sister has always been very strong and unique. This is why I’ve decided to find out what research says about the twin connection. What is it that makes it so different from any other relationship? Why is it so powerful? What exactly, determines this connection? Long story short

Why are twins so close?

Why are twins so close?
I remember my twin telling me, “Let’s ruin the photo by sticking our tongues out!” Needless to say, my silly sister, Laura Heric, is the one on the left. You don’t think the photo was ruined though, do you?

It all starts in the womb.

The first real interaction of every person initiates right after birth. One of the reasons why twins are so close (and different from everyone) is because their bond is established way before, during pregnancy. It can be seen as early as 15 weeks after gestation, through ultrasound.

While inside the womb, twins are observed embracing each other with their hands, faces, and full bodies. In one specific case of twins, a male was observed reaching out to touch the female twin’s face. His sibling responded by engaging in a cheek-to-cheek motion of stroking. A year after their birth, the twins would replicate this behavior by playing a similar game of cheek-to-cheek stroking. This may indicate that the twin connection is established in the womb, and it continues to exist long after birth.

The connection established in the womb is so strong, that twins who have lost their twins at, or before birth, have reported strong emotional distress. Research done on twin loss illustrate these twins to have strong sensations of loneliness and void throughout their whole lives.

The connection established after birth may also determine why twins are so close.

twin connection

When placed together in the same crib after birth, twins are observed touching, hugging, and sucking on each other. This practice, called co-bedding, has demonstrated improved heart rate, temperature, respiratory control, fewer apneic periods, lower oxygen requirements, and greater weight gain in infants.

In fact, this can be easily portrayed with the well-known case called “The Rescuing Hug”. One of the twins, who was in a critical condition, was saved after being placed in the same incubator with her twin.

But research also indicates a very strong connection with another special someone. Let’s look at what John Bowlby has to say about the attachment theory.

Attachment theory

Right after birth, an attachment becomes established between the infant and a particular individual. According to John Bowlby’s Attachment Theory, this attachment is based on the infant’s need for safety and security. As so, this attachment is formed by the primary caregiver, typically the mother, who provides food and comfort. Direct and empirical observation of twins during their first 3 years of life has shown their strong preference over their maternal figure.

However, it has been quite evident that the twin sibling represents a calming and soothing effect, similar to a transitional object when the maternal figure is absent.

Later, at the age of 3, infants finally internalize themselves as separate individuals from their mothers. As so, their interest in other individuals and objects increases. It is about this time that twins become increasingly involved with each other. Consequently, the twin connection becomes strengthened.

According to Ainsworth’s Attachment Theory, attachment is determined by four important features:

  1. Proximity maintenance

The need to maintain a physical closeness with the attachment figure. This figure is looked for when feeling threatened or when an important achievement has been made.

2. Separation distress

Separation from the attachment figure causes acute distress.

3. Safe haven

The attachment figure becomes a “Safe Haven”. The attachment figure represents assurance and comfort in moments of distress.

4. Secure base

The attachment figure provides a sense of security that allows the exploration of the world. For instance, in the Strange Situation Experiment, you can observe how young children who fall into a “safe attachment” feel free to explore a strange new environment only if their attachment figure is nearby and accessible. Similarly, adults tend to be more at ease facing challenges and exploring new leisure activities when they are aware that their attachment figure is nearby.

Now, let’s connect Ainsworth’s Attachment Theory with my personal twin relationship, and why it reflects the twin connection accurately.

Laura and Sarah

Growing up, my sister and I always had a strong need of being close to each other because of one simple reason: we didn’t know what it meant to be apart. We were used to each other’s presence, in such a way that we felt part of each other. I felt her, in a way, like an extension of myself. Everything I did, I did it with her. She was me, and I was her, and we were one.

We didn’t actively choose to be together. It just happened. Our togetherness was simply habituated due to the circumstances of sharing the same grades school, same living environment, and even same interests. We didn’t understand what being apart meant. It would simply be unnatural to consider this.

But then we split…

Our separation initiated in our early 20’s after my sister decided to study abroad. It was a very difficult period for both of us, but I found a way to connect with others and somehow fill that void. My sister, however, was never able to overcome our physical distance, and her level of distress and unhappiness was abysmal and constant throughout the years.

Perhaps it became easier for me because I was a lot more sociable, and a lot more expressive. My sister remained my “safe haven” even if we were physically apart. She was my go-to person for everything. Although having numerous friends, no one could ever take that place. I would just vent with her, and that was it. It became enough for me because that was all there was. My sister, being much more reserved than me, placed me as a “safe haven” in terms of physicality.

I’ll explain myself better. Any time I’d feel bad about absolutely anything, all I had to do was just sit next to her. And the badness would disappear. No speaking, no interacting. Just sitting next to each other, and everything made sense. That was her (only) way of venting with me. So how could she vent if we were thousands of kilometers apart?

We were still, however, able to explore the world and achieve in our careers and all aspects of our lives without having each other breathing behind our backs. In this sense, we were able to support each other from afar, and that was enough for us.

It can then be inferred that the reason why twins are so close may rely on shared experiences that start from the womb, to the first day of preschool, to the last day of high school, and so on…

But are there other reasons why twins are so close?

The Kinship Genetic Theory states that prosocial behaviors are predetermined by genetic relatedness. As so, Monozygotic twins, who share 100% of their genetic component are determined to have a stronger bond than dizygotic or fraternal twins who only share 50% of their genetic component.  

Being female can also determine why twins are so close. A study made in Finland in 2005, established that twin females perceive themselves to have stronger feelings of attachment to their siblings than twin males. But, it’s important to point out that this may be so because females tend to be more sensitive in their relationships. Females are also more likely to express affection.

All that being said, we can conclude that gender, genes, and shared experiences may determine the intensity of the attachment between two individuals. However, these factors remain insufficient when determining why twins are so close. Parents who do not foment the individuality of each twin in a healthy manner, may cause twins to develop split identities.

Split identities occur when twins do not see themselves as separate entities. As so, rivalry — as well as a strong sensation of inadequacy — may emerge. This results in the need to partake distance in order to further develop themselves as individuals.

But having a conflictive twin relationship does not necessarily eradicate the strong connection that only twins are able to experience. Sadly, this is why estrangement among twins may be a strong source of distress and loneliness.

Let’s now look at twins and their relationships with others.

In comparison to non-twins, twins tend to relate quite differently. This is due to the closeness that implies having a twin. This is why twins may feel lonely or misunderstood in shallow relationships. They may also experience difficulty being alone, as it’s not something they are used to.

However, if twins are able to establish separate lives, and strong separate identities, then it becomes easier for them to stand on “their own”.  Their twinship becomes a sort of “fall-back,” as described by Tancredy and Fraley’s study, which is “the tendency to “fall back” on the twinship as a source of safety and security.”

But even after a twin loses their twin because of death, twins cannot shake off their twin, as they are ingrained within them. This is so because twins have two identities, their own individual identity, and the one formed by their twin.  Their shared identity will remain forever. Intertwined identities, if you may.

In fact, this shared sense of self is so strong, that it has been observed that twins tend to be more alike when raised apart than when raised together. This may be suggesting that the presence of a twin may be affecting the formation of their own identities.

Now let’s get back to twins and their relationships with others.

Twins usually try to recreate their twin connection with others because it’s what they’ve learned. It’s the only way of relating that they understand. As so, they seek for strong, and intense, emotional bonds.

Tancredy & Fraley conducted a study in 2006, where they measured how twins generally perceive their relationships. This study concluded that twins are more likely than non-twin siblings to view their sibling as an attachment figure. They are also less likely than non-twins to use their parents as attachment figures.

twin connection

However, twins do not necessarily feel more attached to their sibling compared to other important people in their lives, such as romantic partners or close friends. They are also able to share the top of the attachment hierarchy with other significant people.

In my personal experience…

I always seek to connect in very meaningful ways. In fact, my sister and I always talked about how our closeness made it natural for us to connect with others at a stronger level.  

After life decided to keep us thousands of kilometers apart for quite a long time, I was able to make strong friendships along the way. I’ve had “temporary” besties who filled that role, but always with my sister by my side (not physically, though). My sister, on the other hand, had her husband.

However, being able to replicate our twin connection was nearly impossible, and trying to do so, was quite fruitless. I don’t even try, as no one will ever come —not even remotely— close to her. The sense of security that she provides cannot be replicated because of what science has determined unique by taking into consideration our genetic background and our shared-life experiences. She was, and still is, and always will be, my go-to person, or as in the words of Ainsworth, my “Safe Haven”. She is with me at all times. I’m pretty much stuck with her, whether I like it or not. ??

Now let’s look deeper into how twins usually feel about each other.

In the words of twin expert (and twin herself), Barbara Schave Klein, “Twinship has been characterized as the ideal intimate relationship because of shared feelings, thoughts and experiences.”

Twins do establish the perfect emotional connection right before birth. This connection only keeps strengthening throughout their lives because of circumstances that escape their choice. Only twins understand the beauty of having who is basically, and literally, their other half.

“A twin by definition is the nearest other human to oneself.”

joan woodward

In my personal experience…

I feel like I am one with my sister. We came from one, and we are still, and will always be, one. Whatever troubled her, hurt me, and whatever brought me joy, instantly made her happy. She is me and I am her, and in that sense, we are one with each other.

This sense of belonging and one-ness is a blessing. This love connection is an experience that can only be experienced by those who have twins themselves, and it’s a love so great and so unique because you are born with someone who is genetically imposed to love you as close or even more as their own self, selflessly and unconditionally. Because after all, you came from one. Life-shared experiences further intensify this connection. The twin connection transcends death, and that is a gift. It’s a true love connection, selfless and pure.

That being said, my sister is deeply ingrained in me. Trying to live without her is like denying my own self because she is part of me in a way that no one else could be. The feeling of one-ness, as reported by twins in all these studies, is real. The feeling of belonging, of being one with someone else, cannot be replicated. Everything I do, I do it with her in the back of my mind, as she is always with me, as a part of me. She is me, and I am her. My entire heart belongs to her.

“What it’s like to be a twin? I have been asked this a lot in my life. The best way I can describe it is this:  I have the most beautiful family tree. Four amazing children, an incredible husband, and five of the most beautiful (and spoiled) grandchildren in the world. Anyone who knows me would say I am with them always and would literally give my life for them. Yet . . . by powers outside of my control, they consume only half of my heart. The other half belongs to Neva. We are all we have ever had.”

Eva Jo Sombathy, twin to Neva.

So, why are twins so close?

Twins are genetically-bound to each other. In addition, twins establish a connection before being born and subsequently grow intertwined with each other. They make decisions, overcome challenges, and even cry together. They basically learn how to live together. In this sense, twins share an identity. This is why the twin connection may easily transcend any other connection made in life. Not even death can separate twins.

If you liked our Why are Twins so Close? article, you will like our upcoming article on Twin Loss. Be the first to know of it by subscribing!

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Sarah Peláez is a Clinical Psychologist, Learning Therapist, and author of “The Psychology of Intuition.”

How to reference this article

Pelaez.S (2022). Why are twins so close? PsycheSpot

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