Reared-Apart Twins From the Philippines
When I consider material to present in the News, Views, and Comments section of Twin Research and Human Genetics (TRHG), I am amazed by how many topics there are to choose from. With respect to the current issue, I had to decide among a newly discovered pair of reared-apart male twins (MZA), an overview of concentration camp survivor Annetta Able’s exceptional life (see the Dedication above), and a pair of young monozygotic (MTZ) reared-together twins whose parents are raising one twin in the Jewish faith and his co-twin in the Lutheran faith. Various circumstances and considerations led me to focus on the reared-apart twins with reference to relevant psychological and medical findings. I plan to address the other topics in subsequent issues of this journal, but they could conceivably be replaced by other captivating subjects. Here is how I learned of this recently reunited pair:
On March 28, 2025, Roberta Blake, former editorial assistant of TRHG, forwarded the following message to me: ‘I wanted to ask about the opportunity of being part of a study. I’ve been reunited with my identical twin brother last year. And I’ve been reading more about what that means. I’ve become passionate about twin studies and it would be great to learn more about your research!’
I immediately contacted the sender to learn more about his life history, which I knew would be compelling — I was not disappointed. I will refer to him as CM and his twin brother as PM in the interest of confidentiality. For purposes of this article, I was in contact with CM only. The twins are shown in Figures 1a and 1b.
Figure 1 a and b. CM (left) and PM during their 2023 meeting in the Philippines at age thirty. Photo Courtesy: CM.
CM is two inches taller than his twin and feels that their faces are no longer identical. Height differences between MZA twins in the early reared-apart twin studies ranged between .6−.8 inches (Farber, Reference Farber1981), but can be several inches in selected pairs, most likely reflecting different prenatal effects (Segal, 2017). Interestingly, some MZ twins and their families exaggerate co-twins’ slight facial differences that are imperceptible to people meeting them for the first time. CM completed a standard physical resemblance (Nichols & Bilbro, Reference Nichols and Bilbro1966), but it was inconclusive since items relating to confusion by others could not be answered. I found CM and PM’s photographed faces extremely similar in pictures taken in early childhood and beyond, so I am leaning toward their classification as MZA at present. I forwarded DNA test kits to the twins and will publish the definitive findings in a later issue of this journal when available.
The twins’ separation was unknowingly planned prior to their surprise birth, prompted by family circumstances and cultural practices. The family’s financial instability persuaded the twins’ mother to arrange for the firstborn twin, CM, to be adopted by her sister (the twins’ aunt) who had lost a young daughter to cancer. In their family, it was not uncommon for an aunt to raise a sibling’s child under extenuating circumstances. However, the presence of a second twin caused complications because the twins’ father insisted on keeping him. As a result, CM was raised by his aunt who became his adoptive mother and PM was raised by his biological parents.
CM and his new family did not remain for long in the Philippines — they relocated to Boston, Massachusetts, the city where CM was raised. CM’s birth certificate was altered, naming his aunt and uncle as his parents — he had no reason to believe that the mother and father who were raising him did not give birth to him. When CM was 6 years old, his family visited the Philippines, where he was introduced to an ‘aunt’ (his biological mother) and ‘cousin’ (his twin brother). His biological family resided in a very poor part of Manila, in contrast with CM’s privileged Boston upbringing. Even at age 6 years, CM recalled a sense of ‘something deeper’ when the twins met. His mother wept and lifted him up the moment she saw him; CM said that looking at PM was like ‘looking into a mirror’.
PM escorted CM to his room to show him his toys. Given the language barrier between them (CM spoke English, PM spoke Tagalog), the twins could not converse. This situation reminded me of the reunion of MZ Chinese twins raised apart in Sacramento, California (Mia) and Fresvik, Norway (Alexandra), also at age 6. I was present at their reunion where I observed how well the twin sisters played together despite speaking different languages. However, regardless of their lack of verbal communication, CM felt an immediate bond with his brother despite his unawareness of their true relationship. Before leaving, he cried and asked his adoptive mother to give PM the new clothes she had been purchased for him. ‘Even as a child, I sensed he was part of me.’ It was not until 9 years later, at age 15, that CM learned the truth.
Social media has reunited countless numbers of relatives; see, for example, Segal and Cortez (Reference Segal and Cortez2014). In 2003, PM contacted CM via Facebook to ask if he knew who he was — CM identified PM as his cousin. However, when PM revealed the truth about their relationship, CM’s immediate response matched that of many other reared-apart adult twins. ‘I felt shock, excitement, and a sudden clarity about questions I had carried for years. Out of fear of upsetting my adoptive parents, I did not pursue contact then.’ The twins did not meet in person until 2023 when CM returned to the Philippines.
They met at CM’s hotel and the recognition was ‘immediate’. As CM described it, the ‘conversation came easily, as if we were resuming something rather than beginning it’. His description aligns well with what some other MZA twins have reported — reared-apart MZ twin fireman, Mark Newman, explained that meeting his twin brother, Jerry Levey, after 31 years was like joining him again after a vacation — details had to be provided, but the rapport was instant. My study of reared-apart twins’ relationships showed that MZA twins felt higher levels of closeness and familiarity than DZA twins upon meeting and at the time they participated in the Minnesota Study of Twins Reared Apart (Segal et al., Reference Segal, Hershberger and Arad2003). In addition, nearly three-fourths of the 76 separated MZA pairs from three early studies for whom information was unequivocal (40/54) developed close social relationships soon after meeting (Segal et al., Reference Segal, Hershberger and Arad2003).
CM was introduced to PM’s wife and children and was stunned to see the resemblance between PM’s son and himself when he was younger. In contrast with PM, CM is homosexual — male sexual orientation has a genetic component of approximately 34–39%, as reported by a study of reared-together Swedish twins (Långström et al., Reference Långström, Rahman, Carlström and Lichtenstein2010). Other influences on sexual orientation derive from biological, neurological, and environmental sources (Agha et al., Reference Agha, Antoun, Bacha, Nabbout and El Khoury2025). Homosexuality has been variously identified in MZA and DZA male and female twin pairs, but the numbers are too small to draw firm conclusions about its origins and frequencies (Segal, Reference Segal2012).
PM shared information about the twins’ relatives, including their older sister and younger brother. ‘For the first time, I felt a missing part of myself return’, another common refrain from reunited twins. There is no such thing as prenatal knowledge of twinship; rather, I suspect that most separated twins, who are usually adoptees, do not look or act like the families they lived with. Suddenly, they find themselves among biological relatives whom they resemble in many physical and behavioral ways. CM noted that both twins are naturally reserved, self-conscious about their hair, like the same sleeping position, and consume food quickly. Scores of twin studies have found genetic influences on personality traits (Knopik et al., Reference Knopik, Niederhier, DeFries and Plomin2017). Matched fastidiousness over hair, sleeping position, and speed of food consumption have also been observed in some MZA pairs (Segal, Reference Segal2007; Segal & Montoya, Reference Segal and Montoya2018). I am unaware of formal twin studies of sleeping position or hair care, but a twin study of eating rate in children reported a heritability estimate of .62 (Llewellyn et al., Reference Llewellyn, Van Jaarsveld, Boniface, Carnell and Wardle2008).
MZ twins are never exactly alike, and CM and PM are no exception. Aside from their differences in sexual orientation, CM observed that the twins’ tastes in music and food diverge, a likely reflection of their different rearing environments (Boston and Manila). The twins’ different educational opportunities are also evidenced by their backgrounds and circumstances — CM is working toward a law degree at a prestigious institution, while his brother drives a taxi to support his family. CM’s concluding words truly captured the powerful emotions that most newly reunited twins feel. ‘I did not only find my brother. I found an entire part of my identity that had been written over by a piece of paper [birth certificate].’
Every pair of separated twins leaves lingering question. Both during and outside my email correspondence with CM I wondered: What specific factors allow some reunited twins to connect so closely and quickly, despite a language barrier between them? Why do some families conceal the truth about separating twins after birth? How do twins’ different cultures craft behavioral and attitudinal differences between them? How does learning of twinship in adulthood impact self-concept and other social relationships? The search for answers continues.
Twin Research Reviews
Twin Discordance for Multisystem Inflammatory Syndrome
Multisystem inflammatory syndrome in children (MIS-C) appears following COVID infection. Akçay et al. (Reference Akçay, Oğur, Menentoğlu, Güvenç, Sofuoğlu and Şevketoğlu2022) summarized three cases involving young affected MZ twins whose co-twin showed no MIS-C symptoms despite being infected. Included in the study were a pair of 2-year-old male twins (Case 1), 12-year-old male twins (Case 2), and 10-year-old male twins (Case 3). Symptoms in all three cases included vomiting, diarrhea, and fever. The affected twin in Case 1 also experienced a diffuse rash, while the affected twins in Cases 2 and 3 additionally experienced abdominal pain. Echocardiography showed LV (left ventricle) systolic dysfunction in all three patients — this condition is identified by a weakened heart with the left ventricle unable to contract (or squeeze) normally when the heart beats. The result is that less blood circulates throughout the body (Johns Hopkins Medicine, 2025). The researchers speculated that epigenetic differences between the twins and/or differences in their exposure to viral load explain why one twin failed to develop MIS-C despite testing positive for the infection.
IVF Twins and Hearing Impairment
Hearing impairment in twins has been associated with congenital factors, although age-related loss is more closely tied to genetic influences. Observed differences in hearing between twins who were naturally conceived and those conceived by in vitro fertilization (IVF) have been observed in some studies (Yin et al., Reference Yin, Su, Siyuan, Yin, Wang, Deng and Wang2023). However, a recent investigation did not reveal a difference in the incidence of impaired hearing between these two types of twins (Guo et al., Reference Guo, Liu, Liao, Huang, Tan, Mo, Ouyang, Zhang and Chen2024). In fact, some studies have failed to detect differences in physical growth, motor milestone attainment, and behavioral development between twins conceived naturally or by IVF (van Beijsterveldt et al., Reference van Beijsterveldt, Bartels and Boomsma2011). However, the study by Guo et al. (Reference Guo, Liu, Liao, Huang, Tan, Mo, Ouyang, Zhang and Chen2024) did find older maternal age and a lower incidence of low birth, as well as higher rates of placental abnormalities and placental abruption, among the IVF pregnancies.
Writing Styles of MZ Twins
Authorship attribution is the field concerned with identifying the author of a particular text. A study comparing the writing styles of three sets of identical twin authors — Lev and Austin Grossman, Julia DeVillers and Jennifer Roy, and Peter and Glenn Adamson — were examined by computational analysis (Mohamed, Reference Mohamed2025). The Grossman twins both write novels, and the DeVillers and Roy twins author children’s books, some together and many with twin-based themes. The Adamson twins differ somewhat in their specialties — Peter is a philosopher and historian and Glenn is an historian. Both twins are nonfiction writers. The variables of interest in the study included sentence structure, grammatical patterns, and a number of other features. The investigator found that the twins’ writing styles were not more alike than those of unrelated individuals, but conceded that the small sample size precluded definitive findings. It is also important to note that the zygosity of the pairs was confirmed by ‘personal communication’ rather than by objective scientific methods. This aspect of the study would normally be problematic, given the risk of misclassification; however, my inspection of the twins’ photographs is consistent with their diagnosis as monozygotic twins.
Update on Twins with Feingold Syndrome
Feingold syndrome involves characteristic features of the hands (shortening of the second and fifth fingers; inward curvature of the fifth finger), head (small head; small jaw), and feet (fusion of the second and third or fourth and fifth toes); see Segal (Reference Segal2025). The MZ male twins in question are now 22 months old and making progress. Physically they are mostly caught up in age — they ride a balance bicycle and enjoy climbing and indoor skiing. A recent video recording shows both twins successfully making a basket on a child-size basketball court. They also enjoy music and moving their bodies to the sound. The twins’ speech therapist reports that they are saying 15 to 20 words, and their receptive understanding is good. This past Halloween, the twins won best costume award from a local trick-or-treating event. A significant lingering challenge concerns their eating habits; however, bottles have been replaced by cups and as indicated above, their physical growth is good. They continue to be quite social which pleases their mother greatly. I plan to follow the twins periodically and to report on their development. The twins are shown in Figures 2 and 3.
Figure 2. The twins won best Halloween costume award on October 31, 2025.
Photo courtesy: The twins’ mother.
Figure 3. The twins are enjoying an indoor skiing facility to which the family goes every Saturday. The slopes are small and the twins are able to go down on their own.
Photo courtesy: The twins’ mother.
Human Interest
Conjoined Twin Girls Born in Sri Lanka
Female twins were delivered by Cesarean section at the Castle Street Hospital for Women, in Sri Lanka, in mid-November 2025 (Newswire, 2025). The twins’ mother was 29 years of age. One twin weighed 2.2 kg (4.85 pounds) while their combined weight was 4.4 kg (9.70 pounds). The twins, who are joined at the abdomen, appear to be healthy and in stable condition. They are the first conjoined pair to be born at the Castle Street Hospital, although the director noted that twin births were not uncommon in his facility. The twins will be transferred to a different hospital for evaluation and surgical preparation at age 3 months.
Conjoined Twin Boys Born in Papua New Guinea
On October 13, 2025, conjoined male twins were delivered at the rural Braun Medical Hospital, in the town of Finschhafen, located in the Morobe Province of Papua New Guinea (Waide, Reference Waide2025). Once stabilized, the twins and their mother were transferred by medevac to the capital city of Lae for specialized care at the Angau Memorial Hospital. Two heartbeats had been detected during the pregnancy, but conjoined twinning was not observed until an operation that occurred later. The twins are connected at the lower part of their bodies and share some organs, but they have separate limbs and genitals.
The possibility that they would be sent for surgical separation was under consideration (Fisher, 2025). Then, in early December, the decision was made by their parents to send the twins to Sydney, Australia where the operation would be performed by a multidisciplinary team — the parents are under considerable stress. Unfortunately, the twins will undergo a risky procedure that may sacrifice the life of the one of the infant boys.
Update on Conjoined Minnesota Twins, Abby and Brittany Hensel
The Hensel twins are well known among members of the medical community and general public. Their residence in a small Minnesota city has led to a constant outpouring of support as their parents attempted to give the twins a normal childhood (Zarowski, Reference Zarowski2024). The twins, classified as dicephalic parapagus, share a torso, blood circulation, and some organs, but their brains and spinal cords work independently. Abby, who is on the right side, controls the right arm and leg, while Brittany controls the left (Kaur, Reference Kaur2024). A comprehensive update on the twins at age 34 years is inspirational.
The article traces their life history from birth to the present. Highlights include coordinating their actions for swimming, bowling, volleyball, and driving. In addition, they both earned college degrees at Bethel University in 2012, after which they moved out of their family’s home for a more independent life. The twins toured London with friends and taught there, as well. They have secured teaching jobs at Sunnyside Elementary School, in New Brighton, Minnesota; however, they earn only a single salary since the school reasoned that they were filling just one position. In contrast, they paid one college tuition, while their registration fees were separate (Garik, Reference Garik2025). In 2024, the pair revealed that Abby had married Josh Bowling in 2021. Their life is one of cooperation and compromise that should set an example for other conjoined twins and for the concerned public. Humans are able to thrive successfully under many circumstances and the llives of Brittany and Abby are great example.
Twin Sentenced for Criminal Activities
In 2023, identical twin, Samantha Petersen of Kellogg, Minnesota was driving her SUV in Stewartville and struck a buggy carrying an Amish family. Two children were killed and two were injured. Petersen, who had been driving under the influence of methamphetamines, was sentenced to a 4-year prison term and ordered to pay $40,000 in restitution. At the time of the accident, in a curious twist, the twins arranged for Samantha’s identical twin sister, Sarah, who was not on drugs, to take the blame. However, the story fell apart when witnesses recognized that Sarah’s t-shirt differed from the one Samantha had worn on the scene. I provided other details about this case in a previous issue of Twin Research and Human Genetics (Segal, Reference Segal2024).
Correct Identification of an Identical Twin Culprit by DNA Sequencing
The first case of an identical twin to be convicted of a crime, based on DNA sequencing, has been reported (Schreiber, Reference Schreiber2025). The twin, Russell Marrubio, was found guilty of sexual assault in Woodbridge, Virginia. In the past, the twins’ identical DNA profiles would have stymied this case; however, the twins’ difference in rare genetic mutations led to the culprit. The director of bioinformatics at Parabon Nanolabs noted that identical twins have approximately 8 such differences out of 3 billion bases.
