Not All Twins Are Alike: Psychological Profiles of Twinship

Barbara Klein;  Foreword by Marjorie Ford

Book Code: C7584

ISBN: 0-275-97584-3

Hardcover, 160 pages

Praeger Publishers, Publication Date: 2/28/2003, List Price: $45.95


Endorsement from Muriel Kessler, L.C.S.W., Bc.D.:

"The twin patterns and the conclusions that [Klein] delineates and then supports through case histories are informative, fascinating, illuminating. . . . [This book] will help you to understand what's underneath the . . . surface similarities and differences in the twin patterns whom she studied to reveal the deeper emotional and intellectual issues that twins have to confront and make peace with."




Book Excerpt: Chapter Eight: The Legacy of Twinship

When the life stories of all the adult twins who spoke with me are considered together, some "truths" become evident. This chapter will summarize the most important findings of this study. No one finding is more important than another.

Not All Twins Are Alike

The most obvious finding of this research project is that not all twins are alike. In fact, twins within a pair are very different from one another. Even when twin pairs look alike, talk alike, and enjoy very similar interests, they are still unique people. Some twins actually choose to be different from each other for a variety of personal reasons. Their choices can be, and often are, influenced by the environment, including the parenting they received.

The Twin Bond

Although the bond between twins is unique and different from the sibling bond, there are variations in the emotional bonds that twins share. My research describes four distinct bonding patterns.

*Unit identity is found among twins who have lived through traumatic stress and received inadequate parenting as infants and young children. Two sets of identical twins out of the entire sample of 30 sets of twins manifested this twin bond.


*Interdependent identity is found when twins have limited parenting and are treated as a unit instead of as individuals. No external binding trauma as in unit identity is found. Four sets of twins (one set of identical and three sets of fraternal twins) manifested this twin bond.

* Split identity bond is found among twins whose mothers treat them as polar opposites of one another (good-bad). Three sets of identical twins manifested this twin bond.

* Individual identity is found when parents respond to real individual differences between their twin children and encourage them to function as individuals. Twenty-one sets of identical and fraternal twins manifested this twin bond.

Parenting Twins

Parental attachment and interaction with their infants and toddlers creates the nature of the twin bond. The twin bond, once established, endures throughout the lives of twins. It is a fixed or permanent bond that is exceedingly difficult or impossible to change. I know of no cases where the closeness of this deep bond differed throughout a twin’s life. In other words, young twins who were very close and interdependent remained very psychologically attached to one another as adults. Young twins who fought with each and felt that being a twin was "freaky" were alienated from each other as adults. Twins who were treated as individuals growing up maintained a close bond to one another, as well as their independence, throughout their lives.

Evaluation of the early memories of twins can tell us about the parenting they received, the inter-twin relationship, and the quality of their early lives. Such early memories suggest that the nature of the bond that twins shared is a function of the parenting they received.

Parenting is crucial to the development of the self in infancy and childhood and ultimately to who we choose to become in our lifetime. Parenting provides cohesion to what is inherited and what is malleable by the environment. Aspects of twinship may attempt to replace a lack of parenting, but this bond is not strong enough to completely make up for parental inadequacies.

Raising twins is a difficult hands-on task; as well, it is more psychologically challenging than raising a single child. It is easy for parents to make mistakes when raising their twin children because of the closeness twins share, and sometimes it is not easy to establish real differences between twins. Mothers may be overwhelmed by their twin children and allow them too much time together. Separating twins takes time and energy during a period when mothers are naturally overworked and overwhelmed by their "double trouble" children.

Respecting the twin bond without idealizing it or minimizing it is a complicated process. Twins need to be treated as individuals if they are going to be able to function at their optimal state of development. Otherwise, the over-identification between a pair of twins will limit their capacity to form non-twin-like relationships and to separate from each other. A twin’s sense of individuality makes the process of separating from his co-twin possible in adolescence and young adulthood.

The Untold Story of Twinship

Because of the nature of their intense closeness growing up — twins’ shared language, feelings, and experiences — twins commonly have a great deal of difficulty explaining the experience of twinship as an infant and young child to others. This inability to explain themselves to others is partly due to the reality that twins have spent so much time together they do not necessarily want to learn to explain themselves. As twins grow up, they most likely will lack the motivation and skills to verbalize their privately shared relationship with other people. Oftentimes their "untold story" is inaccurately presented by others, who invariably focus on the outward appearances of twins as adorable "look-alikes" or hard-to-handle "double trouble." Early life experiences of twins have long been misunderstood and misperceived by single individuals.

Onlookers and Twins

The public attention of onlookers is a serious problem for twin children, who can easily be confused or overwhelmed by questions such as, "Are they twins? Who is smarter? Who is better looking? Who is nicer?" Even when alone, the twin may still be besieged with questions such as "Where is your sister or brother?"

As adults, twins are able to speak up and explain how harmful and humiliating these experiences were for them. Adult twins often avoid appearing in public together because it reminds them of these troubling childhood experiences. As well, they resent being entertainment for other people, who years later want to ask the same offensive and ridiculous questions.

Separation Issues for Twins

Separation from each other is an especially difficult problem for twins because they share a deep and intense bond that is based on countless shared and similar experiences in infancy and childhood.

Twins usually are separated into different classrooms when they begin kindergarten because of the current emphasis on developing individuality in twins, which is suggested by school policies, mothers of twins groups, and pediatricians. It is common for twins to share friends and interests, as well as to develop separate interests and friends, in the early school years.

During adolescence, twins actively seek out different interests, friends, and romantic partners, and want to be seen as individuals. In young adulthood, twins begin to live separate lives because they have firmly established separate identities outside of twinship. They still keep in close contact with one another by phone or in person. Maturity provides many more separate experiences for twins, who then develop even more distinct lifestyles that they can share with each other.

The capacity for separating from the co-twin is directly related to the twin bond that is shared. External stress especially tends to bring twins closer to one another. Two sets of adult twins in this study endured the traumatic stress of living through World War II in Europe. These twin sets were closer to each other than twins who did not experience such terrifying events. These survivors of war eventually separated from one another but remained in close contact throughout their lifetimes.

Some adult twins lived through hostile or abusive family situations, and as adolescents and young adults turned away from each other. Although they still felt very close to their twin sibling, they did not spend much time together. In family arguments these twins usually were on different sides, allowing the distance between them to continue to evolve.

Nature versus Nurture in the 21st Century

Segal (1999) suggests that identical twins are closer than fraternal twins. My new research complements my previous work (Identity and Intimacy in Twins, 1983) and contradicts Segal’s hypothesis, because it indicates that both identical and fraternal twins can share similar psychic bonding patterns. Fraternal twins were found to share one of two patterns of twinship — interdependent identity and individual identity. Identical twins were found to manifest unit identity or split identity, as well as interdependent identity and individual identity. The patterns of twinship were determined by the quality of parenting the twins received in infancy and early childhood, not by genetic endowment. More simply stated, identical twins and fraternal twins could share a very close bond or a very conflicted and distant bond, depending on the parenting they received.

Sexual preference cannot be specifically determined by genetics nor environment. Even minute differences in genetic endowment may create differences in sexual choice in a pair of twins. For example, two sets of identical twins chose a different sexual orientation from one another. One set of fraternal twins chose a different sexual orientation. All these twin pairs shared an individual identity twin bond.

The environment, which includes the mother-child interaction and the inter-twin relationship, is crucial to the development of identity in twins just as it is in single children. Genetic endowment provides a strong structure for identity, but what is inherited can be modified by the impact of the bond between twins and the bond between mother and twin. The inter-twin relationship, especially, created differences between twins.

Identity Issues for Twins

Twins have unique struggles with identity. The search for self is overdetermined by the reality of twinship, which focuses on conflicting struggles, such as the eternal battle between competition and sharing, as well as stressful and even traumatic separations.

Twins long to have their own "perfect" identity separate from their co-twin, which their co-twin can accept as legitimate and worthwhile. As well, a twin has a distinct identity as a twin that is very different from his separate identity. In essence, twins have double identities — as twins and as individuals.

It is very difficult to be a twin in a non-twin world. Single people have difficulty understanding the intensity of the bond that twins share as children and adults, and it is not easy to explain the connection between twins. Usually people who are very close to twins, such as husbands, wives, children, or business partners, come to understand the attachment twins share.

In superficial relationships twins often feel isolated or misunderstood, so they relate better to people who can tolerate a close relationship. Twins are experts at intimate relationships because they are used to and enjoy closeness, but they do have difficulty learning to be alone. The closeness and trust that twins share endures throughout their lifetimes, except in cases of split identity twin bond.

Twinship has been characterized as the ideal intimate relationship because of shared feelings, thoughts, and experiences. In actuality, early closeness and sharing can create too much interdependency between twins. Learning to function without one’s twin is a very difficult cognitive and emotional task.

Being a Twin in a Non-Twin World

Even after twins have resolved their conflicts over separation and identity, which always includes privately determining who is who in the inter-twin relationship, there are unresolved issues with non-twins who are close significant others. Twins long to recreate their twinship with others. In essence they want to find another co-twin to keep them company and to share emotional and intellectual intensity. This need for closeness can be disarming and confusing for people who can’t understand this deep motivation for intimacy and understanding. For the twin seeking more closeness it can also be very disappointing, lonely, and confusing.

Usually twins are very close to their romantic partners and children because they are motivated by such deep needs for intimacy, but being a twin in a non-twin world eventually leads to loneliness. Partners of twins may come to understand the deepness of the twin bond, but they cannot duplicate it except in rare cases.


Mental Illness and Psychotherapy

Twins, unfortunately, are at high risk for emotional problems. Twins who are seriously neglected or abused and who are not raised as distinct individuals by their parents can suffer from mental disorders related to depression. Suicide as an outcome of a major depression was noted in one twin whose sister participated in this study. Parents of these twins made no attempt to treat their girls as different individuals. They formed a self-identified and contained unit divided into outgoing/impulsive and responsible/withdrawn. When the impulsive twin became isolated and depressed she had no internal resources to prevent her from suicide.

Twins with a split identity bond suffered from mental disorders. The twin who was treated as the bad one suffered from clinical depression. The twin who was treated as the good one suffered from narcissistic or borderline personality disorder and an eating disorder.

Twins as adults often need to work through issues they have with non-twins and with living in a non-twin world. They seek out psychotherapy, which is highly successful in treating some of their intense need for closeness with others.

Treatment failure was present with three individuals who sought out therapy. These individuals were members of split identity twinships and interdependent identity twinships. Treatment failure was related to complicated distortions in transference and countertransference reactions that stemmed from early twin issues. Therefore, therapists or analysts need to have a strong understanding of twin development if they are working intensively with twins.

Death of a Twin

Many of the twins I interviewed discussed their fears of being alone in the world without their co-twin. The loss of a twin is a very devastating experience for the surviving twin, who can feel like part of herself has also been lost. It is extremely difficult to overcome this type of loss, which affects the personality structure of the surviving twin for the rest of her life. The surviving twin endures the loss of the co-twin by holding onto the memories of their relationship and by not psychologically betraying the lost twin in her thoughts.

Both women who lost their twin sister were deeply affected. Interestingly, both were members of fraternal twin pairs, which suggests that fraternal twins are as close as identical twins and contradicts previous research indicating that identical twins are closer (Segal, 1999).

What Twinship Tells Us About Intimate Relationships

From twins’ life experiences and life stories I have come to understand that real working intimate relationships as compared to fantasies are based on countless shared experiences and healthy competition as well as a capacity to compromise and take care of another person. As part of their birthright twins are forced to share, compete, and take each other into consideration in their daily lives. Single infants and children, even from large families, simply do not make the same basic adjustments in their thinking.

Twins are well seasoned to share and care. They are not fearful nor inhibited as single children may be, because they have confronted their fears about winning and losing so many times. Twins are accustomed to an ongoing process of give and take, of sharing thoughts and feelings, which results in real intimacy. Single people can learn this lesson, too.


I hope my reader has gained some insight into twinship, that twins are more complicated than simply being cute or freaky. Twins share the warm comfort that comes from having someone understand their deepest thoughts and feelings. Twins have an ally who will stand by them through times bitter or fruitful, who will cheer them on and cry with them. Infant twins have a steadfast companion for play and older twins have a perennial colleague, someone to turn to with their questions.

Intense communication about everything around you is not as common for single people who did not grow up with a chatterbox brother or sister. The banter of sharing ideas and getting feedback is an enlivening experience because it provides the sense and the reality that someone is concerned about what you are doing and what decisions you are making and how life — your work, your kids, your husband — is treating you. Twinship can make you more thoughtful because you have someone who will supervise you, or have someone to supervise.

Twins who have not received adequate parenting suffer the disadvantage of being a twin more profoundly than those twins who have received good enough parenting and who have been raised to be individuals. Twins who have not been differentiated as children will always be reliant on their co-twin for all kinds of input. Their psyches and souls are interconnected with each other, which makes them over-identified and narcissistically invested in their twinship throughout their lifetimes. They will not develop a sense of their own emotional boundaries. Because of their over-involvement with their twin they will not develop relationships that are separate from the twinship. Their lifestyles are uniquely twinlike because of their propensity to seek out people who will accept their twinship unequivocally. Their range of experiences in a non-twin world will be very limited.

Split identity twins actually have the opposite problems from twins who are overly close to each other. Because parenting has been so distorted and inadequate, they also suffer more profoundly than twins who have had healthy childhoods. Split identity twins grow up to resent one another because they are angry about being robbed of their individuality and labeled as halves of a whole person. They see twinship as a curse whether or not they get over their disappointment and longing for closeness with their co-twin. Obviously, this pattern of twinship has the most disadvantages. These twins talk about how they hate being twins, and they often hate each other.

Split identity twins have a great deal of difficulty giving up their identity as part of a twin pair. The good twin has an elevated sense of self and entitlement even after he has separated from his brother and established a complete sense of self. The bad twin continually sees himself as inadequate — no matter what the reality of the situation is.

Twins who have been raised as individuals make the most adaptive transitions to adulthood. Although they may have difficulty learning to be on their own without their brother or sister, they are ultimately able to resolve emotional issues related to separation from their co-twin. They actively grapple with being a twin in a non-twin world, but they have the most developed tools to deal with potential problems.

In most twinships the advantages of being a twin outweigh the disadvantages. I am reminded of Peter, a very thoughtful and cooperative twin study participant, who at the end of my interview said, "I never wished that I wasn’t a twin." Even Emily, a participant who thought that twinship was a curse, respected her sister. Many of the twins, too many to name here, cherish their sister or brother and feel that being a twin is a gift.

Twinship is a unique developmental experience that is not as well understood as it could be. Clearly, there are serious risks to being a twin, as well as unique benefits. The reader is invited to make his own conclusions.