Twins of Greece: The International Symposium on Twins and Twin-Related Events
Greek mythology is rich with twins, one reason why Greece was the ideal location for an international symposium on twins (Athena, Reference Athena2024). Apollo and Artemis, twins born to Leto and Zeus, are depicted in scenes on many architectural structures throughout the country. Apollo was the god of music, poetry, and the sun, while Artemis was the god of the hunt, wild animals, and the moon. Twins Castor and Pollux shared their mother, Leda, but had different fathers — Castor was the child of Leda’s husband Tyndareus, whereas Pollux was the child of Zeus. Other twin pairs have also appeared in Greek mythology; for example, Phrixus and Helle, Zethus and Amphion, and Aeolus and Boeotus.
The conception of Castor and Pollux illustrates — or perhaps anticipated — the well-documented reproductive process of superfecundation (Segal et al., Reference Segal, Craig and Umstad2020). This would not be the first time that art preceded science — the first mention of separated twins appeared in the comic drama, Menachmi (The Two Menaechmuses) by the Roman dramatist T. Maccius Plautus (254−184 BC). The first appearance of separated twins in the scientific literature was Paul Popenoe’s case study of MZ twins, Bessie and Jessie (Popenoe, Reference Popenoe1922).
I was privileged to attend the first International Symposium on Twins, held at the University of Crete, in Rethymno, between May 23−24, 2025. Dr Maria Markodimitraki, a professor in the Department of Preschool Education, was the principal organizer of this event. The conference attracted speakers and attendees from the United States, Israel, and Germany, as well as from many locations throughout northern and southern Greece.
The symposium began with an opening address by Dr Markodimitraki. She explained that the focus of the conference was ‘Raising Twin Children: Past, Present, and Future’. Dr Markodimitraki informed us that this theme originated in her own experience as a mother of male-female twins, Giorgio and Ioanna. Maria had just started her doctoral studies when she learned of her multiple pregnancy, responding with mixed emotions — immense joy and excitement, tempered by considerable anxiety and uncertainty. She wondered how she would simultaneously raise two same-age children and complete a doctoral dissertation, but she found a way. Under the supervision of Dr Giannis Kugiumutzakis, Maria’s initial dissertation topic was transformed — her study of infant-father interaction became a study of how twins interact with one another, their parents, and grandparents. This change is not surprising, given that a personal connection to twins has inspired many behavioral and medical science investigators to include twins in their research programs — as a dizygotic (DZ) same-sex twin, I am one of them. A photograph of Dr Maria Markodimitraki surrounded by several conference speakers and participants is displayed in Figure 1.
Figure 1. Speakers and participants at the Twins Symposium at the University of Crete, May 23–24, 2025. Left to right: Bastion Mönkediek, Hila Segal, Elpida Chichliourou, Maria Markodimitraki, Nancy Segal, Ariel Knafo-Noam, and Elissavet Vivilaki.
Photo credit: Conference attendee.
The twins symposium was organized around six key topics. The first topic was ‘From Conception and the Different or Shared Genome to Phenotypic Variation’. Giannis Kugiumutzakis, of Greece, reviewed work on neonatal imitation. Spontaneous and intentional mouth opening by the fetus is followed by imitation of a model within the first 10−45 minutes after birth. This behavior reflects a mix of genetic, epigenetic, and environmental factors. Bastion Mönkediek, of Germany, addressed the interplay of genes and environment with reference to inequalities in life chances. He presented examples drawn from the German Twin Family Panel (TwinLife).
The second topic was ‘Aspects of Twin Development and Education (I)’. I compared general intelligence findings from my ongoing, prospective study of young Chinese twins raised apart with two other twin groups. I showed that the young separated monozygotic (MZ) twins became more alike as they aged (Segal et al., Reference Segal, Niculae, Becker and Shih2021; Segal & Pratt-Thompson, Reference Segal and Pratt-Thompson2024), as did the separated adult Danish twins studied by Juel-Nielsen (Reference Juel-Nielsen1980). In contrast, a sample of virtual twins (same-age unrelated children raised together from infancy) were less alike in general intelligence at their second testing. These findings show that genetic factors and nonshared environmental factors related to overall ability increase, whereas shared family environmental influences wane over the life span.
Dr Joan Friedman, a clinical psychologist from the United States, spoke about twins’ relationships with one another. She focused on growth, individuation, and connection, stressing the importance of treating twins as separate individuals. Her findings were based partly on her own experiences as an MZ twin.
The third topic was ‘In Vitro Fertilization: Medical Innovations and Ethical Dilemmas’. Artistea Magaraki, of Greece, noted that one out of six couples wishing to have children fail to conceive when women reach the age of 35 years. Many such couples seek in vitro fertilization (IVF), a procedure that increases the chances of a multiple pregnancy. Given the physical risks of bearing more than one fetus, many European nations have imposed restrictions on the number of allowable embryo transfers.
The fourth section centered on ‘Aspects of Twin Development and Education (II)’. Dr Hila Segal, of Israel, presented findings on relationship dynamics between twins and classroom placement decisions. She generated a series of closeness-conflict and dependence-rivalry relations that inform placing twins together or apart at school. Twins sharing educational settings throughout the day had close relationships, whereas those who spent less time together showed increased conflict; Dr. Segal wisely noted that cause and effect coldl not be discerned at this time. Zygosity was recognized as one of several factors that should be considered when deciding twins’ classroom placement, given that MZ twins are generally closer to one another than DZ twins.
Dr Ariel Knafo-Noam, also from Israel, discussed findings from a longitudinal twin study of values. Twins were assessed by questionnaire at ages 3 through 17 years. He found that individual differences in value stability and changes are partly heritable, and that early temperament predicts values as twins approach adolescence.
The fifth topic was ‘Twins’ Imitation with Important Others’. Dr Markodimitraki presented findings and video recordings of naturalistic interactions between and among twins and parents. She indicated that imitation — vocal, motor, facial, and nonverbal — emerges as a primary means by which infants recognize and respond to the emotional expressions of others. Imitation and early experiences serve as foundational mechanisms in shaping twins’ developing emotional identity. Maria also found greater synchrony in mother-nontwins relations than in mother-twin relations. This finding might reflect more frequent, but shorter, mother-twin interactions. This pattern has also emerged from observations of parent-child verbalization in studies of twins during childhood (Conway et al., Reference Conway, Lytton and Pysh1980; also see Segal, Reference Segal2017).
Maria revealed the striking fact that Greece was cited in Guinness World Records for having the highest increase in twin births among nations. In 1978, twins occurred in 16.5/1000 Greek births, a figure that rose to 57.2/1000 births in 2021. This is probably a function of delayed maternal age (associated with DZ twinning) and greater use of IVF.
Maria Pateraki, from Greece, also described imitation in infant twins. She conducted naturalistic observations of 99 DZ twin and nontwin infants. Her findings matched those in previous studies that found twin versus non-twin differences in imitation.
The sixth and final topic was ‘Twins in Life and Art’. I presented findings from my research on two accidentally switched MZ male twin pairs from Colombia, South America (Segal & Montoya, Reference Segal and Montoya2018; Segal et al., Reference Segal, Montoya and Becker2018). The twins were raised believing they were DZ twins, until they learned the truth about their birth at age 25. One unrelated pair was raised in the city where educational opportunities were plentiful, while the other unrelated pair was raised in the county where educational opportunities were extremely limited. Each twin completed two ability tests — the Wechsler Adult Intelligence Scale (WAIS-IV) and Raven Advanced Progressive Matrices (APM). The city-raised twins outscored the country-raised twins on both protocols and obtained scores that were closer to their unrelated brother than to their MZ co-twin. Most, but not all, reared-apart MZ twins (raised in middle class homes) have generally scored close to one another in ability tests, suggesting that each twin seeks resources and opportunities compatible with their genetic backgrounds. In contrast, the Colombian twins are an excellent example of extreme environments overwhelming genetic potential.
The next speaker was Dimitris Antonakakis, from Greece, who discussed dimensions of twinship in development and musical creativity. He showed films of twin toddlers and asserted that the spontaneous process of sharing has evolutionary and ontogenetic roots in communicative musicality, imitation, and co-regulation.
Antonakakis’s presentation was followed by a film, Growing Up Together, featuring the identical Kapsetaki twins, Marianna and Stefania. Mariana is a neurobiologist, Stefania is a biologist, and both twins are classical pianists. The closeness of their relationship was evident in their shared interactions. Seeing such twins, even in film, leaves a lasting impact on audiences who are impressed with the intertwining of identical twins’ lives.
The final speaker was Elpida Chochliourou, from Greece. Separated as an infant from her twin sister, Maria, Elpida had denied her adoption situation from the age of 12 and for many years after that, despite being prompted at times to recall having been adopted. She argued persuasively that adoption therapists are needed to help adoptees manage their fragmented memories that can profoundly influence their emotional wellbeing and personal identity. Her autoethnographic account was riveting. Despite being the last speaker at the end of two very full days, her audience remained interested and continued to pose questions.
The Twins Symposium concluded past the designated hour, testimony to the high quality of the contributors and contributions, and the excellent organization by many faculty and students. I should acknowledge identical twins, George and Agisilaos Marinakis, who assisted speakers with the audiovisual system; see Figure 2. I was fortunate to speak with them several times and was impressed with their strong bond that means so much to them. Highlights from the conference were also covered by a local television station (KritiTV, 2025) and newspaper (Goodnet, 2025).
Figure 2. Identical twins, George (left) and Agisilaos (Agis) Marinakis (right).
Photo credit: Nancy L. Segal
Two special social events took place during the symposium. Speakers were treated to a live dance performance by Dr Markodimitraki’s twin daughter, Ionnia. Ionnia is an attorney as well as a talented dancer. One evening, speakers gathered for a festive Cretan meal at the local restaurant Avli.
Conference Concluded: Further Travels
At the conclusion of the conference I traveled to Hersonissos, a seaside area in the northern part of Crete. There I met Maria’s twin son, Giorgio, who was working as a summer waiter and plans for a career in hospitality. I noted that he and his twin sister are pursuing different occupations, consistent with the relevant twin literature on vocational interests (Schermer & Vernon, Reference Schermer and Vernon2008).
My next stop was Chania, a city in the northwestern part of Crete. Chania was once the capital of Crete. I was there to deliver a lecture on my work with the twin children who survived the brutal medical experimentation at the Auschwitz- Birkenau death camp, in Poland (Segal, Reference Segal2023). My host was Anja Zuckmantel, executive director of the Etz Hayyim synagogue. This synagogue, the only one in Crete today, was destroyed during World War II, as were others in Chania. However, it is the only one to have been rebuilt, due to the efforts of a long-term resident, artist and museum curator, Nikos Stavroulakis (1932−2017). Prior to the war, Chania was a vibrant Jewish community, as evidenced by my tour of the Jewish quarter.
My next stop was Patras, the third largest city in Greece, located in the western part of the country, in the northern Peloponnese. I traveled there to visit the separated MZ female twins, Elpida and Maria whom I had met personally for the first time at the symposium. (I had written about these twins in an earlier issue of Twin Research and Human Genetics after Elpida had contacted me in 2022 to discuss her adoption history, separation from her twin, and reunion; see Segal (Reference Segal2022). I did not know she was scheduled to speak at the conference until the day before it began. The twins, now 51, were reunited in 2005 at the age of 31. The opportunity to spend several days with them in a more relaxed atmosphere allowed me to follow up on themes that Elpida had raised in her presentation. I will include these new insights in forthcoming books I am currently writing. The twins are pictured in Figures 3a and 3b; note the fortuitous discovery of the ‘Twins II’ sign that frames the twins in Figure 3a.
Figure 3. (a) Reunited identical twins, Elpida Chochliourou (left) and Maria Christodoulopoulou (right).
Photo credit: Nancy L. Segal.
(b) The twins, Elpida (left) and Maria (right), look more alike when their hairstyle is the same.
Photo courtesy: Elpida Chochliourou.
I returned to Athens for the last few days of my trip. I was scheduled to deliver a lecture, ‘Twins: The Science and the Fascination’, at the American College of Greece. My host was Dr Chrysanthi Nega of the Department of Psychology. This was also an opportunity to meet Greek undergraduate and graduate students and faculty and to learn more about the research projects being conducted. Then, later that day, I had an unexpected appointment that was arranged quite quickly.
Just a few days prior, I had received an email message forwarded to me by Twin Research and Human Genetics’ editorial assistant, Roberta Blake. I learned that Aggeliki Siomou, a woman from Euboea, Greece, outside Athens, was searching for her twin sister. Her mother had been told that one of her twin infants had died at or shortly after birth; however, there was no record of the infant’s death. Family members recall inconsistencies and secrecies surrounding the delivery. Aggeliki had tried to find her twin by consulting staff at the Roots Research Center (an organization dedicated to promoting the rights of children in alternative care and the rights of adult adoptees; see Roots Research Center, 2018), examining relevant databases, consulting with her attorney, and enrolling in 23andme and ancestry.com to see if she might discover a match. Still, she wondered what else she might try. Her timing was perfect since I was in Athens; I invited her for a meeting at my hotel. We discussed the possibility of adding her photograph and life history to social media platforms, contacting the department of motor vehicles that issues driver registrations, and hiring a private investigator.
I promised Aggeliki that I would include some of her personal details in this article, in the event that a reader might know of her twin sister. The twins were born on November 11, 1975 — this was the period (1960−1980) during which many illegal adoptions took place in Greece. Aggeliki agreed to have me include her photograph in this article, shown in Figure 4. Aggeliki is now age 49 years, 155 cm tall, and right-handed. Her natural hair color is dark brown or black. She is a makeup professional in the city of Karystos, located on the island of Euboea, not far from Athens.
Figure 4. Aggeliki Simiou, a twin in search of her sister.
Photo credit: Nancy L. Segal.
As our conversation ended, I asked Aggeliki to tell me how she feels on her birthdays. She senses that something is missing — that there is a part of herself that is incomplete. This is a common theme among separated twins. This feeling is often attributed to having been adopted and wondering about one’s biological roots; however, Aggeliki was raised by her biological parents so this explanation does not apply in her case. Of course, there is no such thing as intrauterine knowledge of twinship — Aggeliki did not know she was a twin until her 12th birthday. Now that she knows she is a twin she cannot help wondering what might have been and what still might be …
A fitting end to my travels was discovering and watching the 2022 film Divertimento on board the plane to Los Angeles. Based on real events, the film tells the story of DZ twin sisters, Zahia and Fettouma Ziouani, from the suburbs of Paris, whose passion for classical music led them to create an orchestra.
Twin Research Reviews
Twins’ Neonatal Outcomes
The effects of antenatal corticosteroids on the health outcomes of infant twins were examined by an international collaborative team (Socha et al., Reference Socha, McGee, Bhattacharya, Young and Wang2022). The researchers conducted a systematic review of records (nonrandomized trials), gathered via Medline, PubMed, EMBASE, and the Cochrane Library, from inception to August 12, 2021; 18 studies met the inclusion criteria. They reported that antenatal corticosteroids were associated with reduced infant mortality and respiratory distress syndrome. In contrast, results were inconclusive for other adverse outcomes, such as intraventricular hemorrhage and retinopathy of prematurity.
Growth Discordance and Growth Restriction
Determining the optimal time to deliver twins is a complex decision, especially in the event of fetal growth restriction (Koch et al., Reference Koch, Burger, Schuit, Mateus, Goya, Carreras, Biancolin, Barzilay, Soliman, Cooper, Metcalfe, Lodha, Fichera, Stagnati, Kawamura, Rustico, Lanna, Munim, Russo and Li2022). Using studies published between 2015 and 2018, the final collection of cases included 20 cohort studies with reports of twin pairs’ chorionicity — 7474 pairs were dichorionic and 2281 pairs were monochorionic. The risk of perinatal death per gestational weeks was calculated. It appeared that risks of stillbirth and neonatal death were higher when both twins were small for gestational age and/or showed increased levels of growth discordance. However, the optimal time for delivery was unaffected by growth disorders alone.
Twins’ Romantic Partners and Alcohol Use
Associations between alcohol, smoking, and a range of behavioral measures were examined using data from FinnTwin 16, a population-based study in Finland (Stephenson et al., Reference Stephenson, Cooke, Barr, Maes, Latvala, Piirtola, Silventoinen, Rose, Kaprio, Dick and Salvatore2025). Researchers obtained self-reported information from the romantic partners of twins regarding alcohol consumption, smoking, personality, educational attainment, religiosity, and psychological stress. They determined that having a romantic partner who engaged in drinking and smoking led to a similar pattern in the twins. Partner drinking and smoking also moderated genetic effects on drinking. Finally, it was observed that genetic influence on binge drinking was higher when partners indicated less frequent alcohol use, more frequent smoking, reduced conscientiousness, and higher levels of extraversion, neuroticism, and psychological distress.
Human Interest Stories
The Paget Twins’ Extraordinary Lives
A stunning new memoir about the high society Paget twins, Celia and Mamaine, born in 1916, in Woodbridge, Suffolk, England, was recently released. The author is Ariane Bankes (Bankes, 2025), daughter of one of the twins (Celia). After her mother’s 2002 death, Bankes discovered the twins’ diaries and letters stored in an old trunk. Using these materials, she reveals the fascinating story of the twins’ rearing by their widowed father, their subsequent rearing by relatives, their education, and their entrance into the intellectual and cultural excitement of various European cities, e.g., London and Paris, during the mid-twentieth century. The twins were part of social circles that included writers (Albert Camus and George Orwell), philosophers (Bertrand Russsell and A. J. Ayer) and various intellectuals and artists (Jean-Paul Sartre, Simone de Beauvoir, and Arthur Koestler). Even while their relationships, marriages and work often separated them by great distances, they maintained an extremely relationship to one another, often addressing each other as ‘Twinnie’.
Museum Wing Honors the Lost Rockefeller Twin
The redesigned Michael C. Rockefeller wing of New York City’s Metropolitan Museum opened on May 31, 2028 (Cotter, Reference Cotter2025). This collection includes over 1700 artistic works from Africa, the Americas, and Oceania. A noteworthy display is a group of 15-foot-high carved wooden Asmat funerary poles — they were acquired in 1961 by Michael Rockefeller, the late twin son of former New York governor Nelson Rockefeller and twin brother of New York clinical psychologist, Mary Rockefeller. Michael’s boat capsized off the coast of New Guinea in 1961, but his body was never discovered. The new museum wing is a tribute to his memory.
Remarkable Conjoined Twins in India
On May 13, 2025, a rare pair of conjoined twins was delivered to a first-time mother, at the Bahrat Ratna Dr Babasaheb Ambedkar Hospital, in Kandivli (The Times of India, 2025). The twins were delivered by emergency C-section and transferred to the Sion Hospital for intensive care. Conjoined twinning had not been previously detected, either at a different hospital or at a private clinic. The twins were classified as thoracopagus, because they are attached at the chest; however, they have two separate heads. The sex of the twins was not given. Both twins were placed on ventilators given their critical physical condition.
Death of an Australian Sports Icon
In May 2025, Australia lost a football icon who was also an identical twin (ABC News, 2025). Adam passed away just several months after his identical twin brother, Troy — also a sports icon — died of suicide, a devastating blow to Adam. Adam was just 41 years old and had played for the West Coast Eagles; his twin brother had played for the Brisbane Lions. At the time of his death, Adam was retired from football and was working as a development coach and head of female football. It tuned out that Adam’s life also ended by suicide (Ryan, Reference Ryan2025).
A study by Song et al. (Reference Song, Larsson, Fang, Almqvist, Pedersen, Magnusson and Valdimarsdottir2020) found an increased risk of psychiatric disorders among identical twins who lost a co-twin (due to various causes), relative to fraternal twins and non-twins, in that order. Ten years earlier, I conducted a study showing that identical twins whose co-twin had suicided were more likely to engage in suicidal attempts than fraternal twins whose co-twin had suicided (Segal, Reference Segal2009). In contrast, suicidal attempts did not differ between identical and fraternal twins whose co-twins had died from nonsuicidal causes. These findings suggest a genetically based risk for suicide and related behaviors.
A Most Unusual Triplet Birth
Arnon Martsifer, a single man living in Israel, wished to create a family (mako.com, 2025). He became the father of triplets with eggs donated by a woman in the nation of Geogia and fertilized with his own sperm. The triplets included two male infants and one female infant — Ido, Daniel, and Gali respectively — born at 35 weeks into the pregnancy. It was puzzling that only two embryos were implanted, suggesting that one of the embryos had divided in the womb; however, the triplets were fraternal. After several weeks it was discovered that one of the babies (Daniel) was not conceived by Arnon — DNA tests determined that Daniel was most likely conceived with an egg released naturally by the surrogate and fertilized by her partner at, or about, the time the other two embryos were transferred. Sadly, for Arnon, who had been caring for and becoming attached to Daniel, the child was ultimately given to the surrogate. ‘The feelings were terrible, literally … losing a child. I had no more tears to cry.” Arnon hopes that his two children can meet Daniel in the future. ‘There’s still time for that,’ he said.
When Arnon returned to Israel from Georgia with his children he was forced to take up residence in a hotel — his home at Kibbutz Or Haner (‘Candelight’) near the Gaza strip had been heavily bombed on October 7, 2023. His entire community had been evacuated for six months. Note: I wish to acknowledge my colleague, psychology professor Dr Hila Segal, who notified me of this unusual case and assisted with translation.
