Most Unusual Twin Pairs: A Look at Uterus Didelphys / Twin Research Reviews: Prenatal Aneuploidy Screening for Twin Pregnancies; Twin Conceptions by Same-Sex Male Couples; Legal Personality of Conjoined Twins; Twin Study of Cannabis Use / Human Interest and Importance: Being Taken for Twins Saved Sisters; Twin Children of Jailed Nobel Prize Winner; British 'Biracial' Twins; Triplets Born at Start of Russian Attack on Ukraine; Twins Born in Different Years.

A review of an unusual twin type-twins born to women with two uteri (uterus didelphys)-is presented. This review is followed by summaries of recent research and perspectives concerning prenatal aneuploidy screening for twin pregnancies, twin conceptions by same-sex male couples, legal personality of conjoined twins, and a twin study of cannabis use. Interesting information about twins that has appeared in the media is also presented, namely how being taken for twins saved a pair of sisters; twin children of a jailed Nobel Prize winner, British 'biracial' twins, triplets born at the start of Russia's attack on Ukraine, and twins born in different years.

Partnership with the University of São Paulo Panel of Twins: A Four-City Tour and More / Twin Research Reviews: Twin Research on Binge Eating; Twins' Physical Outcomes Linked to Different Diets; Working Conditions and Sickness Absence in Swedish Twins; Facial Morphology Differences in Monozygotic Twins / Human Interest and Importance: Michigan Family Forced to Adopt Their Own Twins; Ethics of Hiring a Surrogate to Bear Twins; Twin Survivors of the Israel-Hamas War; Twin Pregnancy with Double Uterus; Three Twin Pairs on Same Women's Soccer Team.

This article begins with an overview of twin research in Brazil, initiated by the University of São Paulo Panel of Twins. I met with many new research collaborators and students while on a fall 2023 four-city lecture tour in that country. A meeting with a world-famous surgeon who recently separated craniopagus conjoined twin pairs is also described. This overview is followed by summaries of twin research on binge eating, twins' physical outcomes linked to different diets, working conditions and sickness absence in Swedish Twins and facial morphology differences in monozygotic twins. The final section of this article provides a sampling of human interest stories with important implications. They include a Michigan family forced to adopt their own twins, ethical issues surrounding the hiring of a surrogate to bear twins; twin survivors of the Israel-Hamas war, a twin pregnancy with a double uterus, and three twin pairs on the same women's soccer team.

Assortative parenting and assortative cross-parenting: New views of parental preference for selected children.

Two novel parenting terms are introduced into the literature on parent-child relationships. The first term, assortative parenting, references a familiar, but poorly defined concept regarding parental affinity for a given child. The second term, assortative cross-parenting, denotes a previously unrecognized relationship phenomenon, namely parental attraction to a child who displays favored qualities expressed by the parent's partner. These terms derived from interviews with same-sex couples, but easily apply to heterosexual couples, as well. The proposed concepts and labels should initiate new lines of inquiry that can illuminate unstudied aspects of family dynamics. Given that improved reproductive techniques and revised societal attitudes are continually creating novel family structures, studies of personal relationships and the families in question would benefit by admitting these concepts into ongoing research programs.

Born Apart, but Raised Together: Twins Delivered in Different Countries/Twin Research Reviews: Hallermann-Streiff Syndrome in Monozygotic (MZ) Twins; Effects of Technology on Conjoined Twin Separation; Reciprocal DIEP Transplantation Between MZ Twins; Guidelines for Multifetal Management/Media Reports: Book by World's Oldest Auschwitz-Birkenau Twin Survivor; Passing of Ian Wilmut; Zhores Medvedev Was an Identical Twin; More Gay Fathers with Twin Sons; Twins and Siblings Admitted to Medical School; First and Fourth Records for Major League Baseball Twins.

The circumstances and subsequent life events of the first twins to have been born in different countries are examined. Given that both twins were born in the United Kingdom, their common citizenship was never questioned. In contrast, twins born in Canada to a legally married gay transnational couple - composed of one American and one Israeli - were assigned as citizens of different nations and their parents were regarded as if unmarried. This essay is followed by reviews of research on the Hallermann-Streiff syndrome in monozygotic (MZ) twins, the effects of technology on conjoined twin separation, reciprocal deep inferior epigastric perforator (DIEP) transplantation in MZ twins and new guidelines for managing multifetal pregnancies. Finally, media reports on a book by the world's oldest Auschwitz-Birkenau twin survivor, the passing of Dr Ian Wilmut, the identical twinship of Zhores Medvedev, another case of gay fathers with twin sons, twins and siblings admitted to medical school, and the first and fourth records for major league baseball twins are presented.

The 18th International Twin Congress, and a Look at Twin Research in Wales/Twin Research Reviews: Temperamental Similarities and Twin Relations; Maximizing Twin Designs; Rare Tubal Ectopic Pregnancy; Twins' Academic Self-Concept Formation/In the Media: Identical Infant Twins Reunited; Birth of Identical-Fraternal Quadruplets; Identical Twin Comedians; 'Twice in a Lifetime': Meeting an Unrelated Look-Alike; Twins in the Tour de France.

The 18th International Society for Twin Studies convention took place between June 15-17, 2023, in Budapest, Hungary. A selective sampling of highlights from the meeting are presented. This is followed by a brief overview of ongoing twin research at the University of Aberystwyth in Wales and some twin treasures in the National Library. Next, reviews of timely research that examine temperamental similarities and twin relations, the maximization of twin research designs, a rare ectopic twin pregnancy, and twins' academic self-concept formation are presented. The final section covers stories appearing in various media sources that are informative, enlightening, and interesting, namely a reunion of identical infant twins, the birth of identical-fraternal quadruplets, identical twin comedians, meeting an unrelated look-alike, and twins in the Tour de France.

Twin Research and Human Genetics - News, Views & Comments: Memoirs and Autobiographies by Twins: Research Angles and Human Interest/Twin Research Reviews: Fetal Reduction in Twin Pregnancy; Twins' Personality and Military Service; Growth Restriction in Twins; Advances in Conjoined Twin Separation/Media Reports: Update on Scientist Who Performed Gene Editing on Twins; Twins From 33-Year-Old Embryos; Twins' Outcomes From Dietary Differences; Fraternal Twins With the World's Largest Height Difference; Twin Home Experts Conquer Rat Infestation.

Twins' memoirs and autobiographies both enlighten and entertain. These works, often overlooked by researchers, may suggest new avenues for investigation, such as nonshared environmental events that propel twins in different directions. Of course, MZ twins' generally parallel experiences and DZ twins generally criss-crossing paths are the bases of fascinating life stories. The following sections examined recent research on fetal reduction in twin pregnancy, twins' personality and military service, growth restriction in twins, and advances in conjoined twin separation. This article closes with reports of a scientist who performed gene editing on twins, a twin conception from 33-year-old embryos, twins' physical outcomes from dietary differences, fraternal twins with the world's largest height difference and the Twin Home Experts who conquer rat infestation in New York.

Role of Twins in Waardenburg Syndrome: 1916 - present/Twin Research Reviews: MZ Twins' Different Dermatoglyphics; Twins with Sagittal Suture Crainosynostosis; Blood Pressure in Female Twins; MZ Twins' Education and Political Knowledge/Media Reports: Twins Created by Reciprocal In Vitro Fertilization; Reared-Apart Triplets' Limited TV Series; Abducted Twin Infants; Winkelvoss Twins Charged by the Securities and Exchange Commission; Going From 'Me' to 'We'.

Waardenburg's syndrome involves deafness accompanied by various visual difficulties. The role of twins in identifying this disorder and advancing understanding of its origins and symptoms is described, beginning in 1916 and continuing to the present. This overview is followed by current research on monozygotic (MZ) twins' different dermatoglyphic features, twins with sagittal suture crainosynostosis, blood pressure in female twins, and MZ twins' education and political knowledge. The final section presents media reports describing controversies surrounding twins created by reciprocal in vitro fertilization, reared-apart triplets' limited TV series, abducted twin infants, the Winkelvoss twins' charges by the Securities and Exchange Commission, and going from 'Me' to 'We'.

Handedness in twins reared apart: A review of the literature and new data.

Reared-apart twin studies are a powerful means for identifying the relative contributions of heredity and environment to variation in human physical and behavioural traits. One such characteristic is handedness, for which it has long been noted that approximately 20% of twin pairs are comprised of one right-handed cotwin and one left-handed cotwin. Reared-together twin studies suggest a slightly greater concordance in monozygotic (MZT) than dizygotic (DZT) twins, implying that genetics influences hand preference. We report here two studies of handedness in reared-apart twins. Study 1 synthesizes the available data and estimates that at least N = 560 same-sex reared-apart twin pairs (for which zygosity is known with reasonable confidence) have been identified. Of these, handedness data are available for both members of n = 415 pairs. We observed similar levels of concordance/discordance for reared-apart monozygotic (MZA) and dizygotic (DZA) twins. However, although direction of handedness (right or left) has frequently been examined, strength of handedness (strong or weak) has not. Study 2 examined strength of hand preference and relative hand skill, as well as right- and left-hand speed, information available for participants in the Minnesota Study of Twins Reared Apart (MISTRA). We provide evidence of heritability for right-hand and left-hand speed. We also found hand preference strength was more alike than chance in DZA, but not MZA, twins. Findings are discussed in relation to genetic and environmental influences on human handedness.

From the Library of the Late Irving I. Gottesman: Memories and Treasures/Twin Research Reviews: Twin Study of Callous-Unemotional Traits; Depressive Symptoms in Prospective Chinese Twin Mothers; Twins With Sagittal Suture Craniosynostosis; Creative Expressiveness and Educational Achievement/Media Reports: Male-Female Twin Holocaust Survivors; Nontuplets Born in Mali; Indian Twins Marry Same Man; Twins Born From Longest-Frozen Embryos; Infant Twin Abduction; Twins Born in Different Years.

The experience of going through the personal library of our late esteemed twin research colleague, Dr Irving I. Gottesman, is described. I came away with fond memories and unexpected treasures. This essay is followed by brief reviews of timely research on factors affecting callous-unemotional traits, depressive symptoms in prospective Chinese twin mothers, twins with sagittal suture craniosynostosis, and creative expressiveness and educational achievement. Media reports on informative topics of interest to researchers and the general public include male-female twin Holocaust survivors, nontuplets born in Mali, Indian twins who married the same man, twins born from the longest frozen embryos, an infant twin abduction and twins born in different years.

Senatorial signatures Absence of male-female differences in left-handedness.

A greater frequency of left-handedness among males than females has been observed in general populations. Past studies have explained this difference with reference to males' greater susceptibility to adverse birth events, while more recent studies have identified other contributing factors. On January 16, 2020, U.S. senators signed an oath to act impartially during the president's impeachment trial. This televised event allowed direct comparison of the proportion of right-handedness and left-handedness in a professionally accomplished sample of males and females. As expected, no sex difference in the proportion of left-handed senators was found, although the small sample size offered low statistical power. Replicating this finding with a larger sample would support the view that left-handedness among select groups of males is linked to genetic factors.

Twin Artists: Unique Sources of Inspiration and Talent/Twin Research Reviews: Ethnic and Racial Factors Affecting Type of Twin Delivery; Outcomes in Twins Conceived Naturally and With Reproductive Assistance; Delivery Time for Growth-Discordant Twins; 3D Study of Twins' Facial Resemblance/In the Media: Baseball Players With Divergent Careers; Basketball Twins in the Elite 8; Twins' Grave and Epitaph; Twins Conceived Three Times in 2 Years; Twins in the Hockey Hall of Fame; Superfetated Twins.

The unique sources of artistic inspiration and talent of twin artists are examined. The professional literature is rich with twin studies of creativity, but lacking when it comes to specific artistic domains - for example, painting and sculpting. The section that follows provides reviews of current research on ethnic and racial factors affecting type of twin delivery, pregnancy outcomes when twins are conceived naturally or with reproductive assistance, the effects of intrauterine growth discordance on the timing of twin delivery, and three-dimensional (3D) assessment of twins' facial resemblance. The final section summarizes information about twins in the media. The stories include twins distinguished for both baseball playing and physical injuries, twins who reached the National College Athletic Association's Elite 8, a twin pair's grave and epitaph, a mother who conceived twins three times in 2 years, twins in the Hockey Hall of Fame, and a set of superfetated twins.

Reared-Apart and Reunited: Extraordinary Dynamics/Twin Research Reviews: Twin Bereavement and Lifespan Associations; Identifying Novel Mutations in Twins; Parenting Premature Multiples; Conjoined Twins in Cross-Cultural Context/In the News: Madeline Albright, Mother of Twins, Passes Away; Identical Twin Songwriters Compose New Musical; Visually Impaired Twin Skiers; Identical Twin Brothers Undergo Heart Transplants; Naming the Genain Quadruplets.

The focus of this article is on insights gained from the extraordinary dynamics that took place between a pair of reunited monozygotic female twins from Greece. Topics include visualizing the co-twin prior to meeting, the unique love and attraction between the twins, a mother's response to discovering her child's cotwin and the challenges posed by insufficient kinship categories. The following section of this article surveys four recent twin research reports. They include Bereavement and Lifespan Associations; Novel Mutations in Twins; Parenting Premature Multiples; and Conjoined Twins. The final part of this article presents interesting and informative news about twins from popular sources. The topics covered are the passing of Madeline Albright (Secretary of State and mother of twins); identical twin songwriters; visually impaired twin and sibling skiiers; identical twin brothers who both received heart transplants; and the naming of the Genain quadruplets.

Twins' Continuing Tales: New Evidence Reshapes Thinking/Appreciation and Recognition: Honoring Colleagues, Honoring Twins; Remembering Colleagues, Remembering Twins / In the Media: Ukrainian Twins in Wartime; Twins Born in Different Years; Identical Twin Surrogate; A Quaternary Family; Abducted Twins in Serbia.

Twin research proceeds at a rapid pace, with new findings constantly modifying our knowledge and thoughts about many issues. In the present article, this concept is applied to the writing of books and articles about twins, with special emphasis on the author's recent experience. My lead essay in most contributions to the News, Views and Comment section of this journal is usually followed by a review of current research findings; however, significant events necessitated a departure from this format. At this time, it is important to both honor and remember colleagues and twins, both past and present. The final entry in this article highlights media events that variously pose biological and social implications for our field. They include the hardships of Ukrainian twins during wartime; twins born in different years; identical twin surrogacy, a quaternary family and abducted twins in Serbia.

The 2021 Congress of the International Society for Twin Studies: Twin Research at the Cutting Edge/Twin Research: Maternal Bonding with Twins; Twins with Peters Anomaly; Selective Termination in Dichorionic Twin Pairs; Neuropsychological Function in Twins with Neurofibromatosis/News Reports: World's Most Premature Survivor - A Twin; Twins Confuse Giants' Baseball Fans; Malaysian Twins Switched at Birth; 'Biracial' Twins.

Selected highlights from the 2021 Congress of the International Society for Twin Studies are reviewed. The perspectives of a new graduate student member to the society are also included. Timely research covering issues related to maternal bonding with twins, twins with Peters anomaly, selective termination in dichorionic twin pairs and neuropsychological functioning in twins with neurofibromatosis is reviewed. The final part of this article includes interesting and informative media reports related to the world's most premature survivor who is a twin, identical male baseball players, Malaysian twins switched at birth and a pair of the so-called 'biracial' twins.

Quadruplets: Risks, Outcomes and a Set of Four/Twin Research Reviews and a Lawsuit: Antenatal Corticosteroids and Twins' Neonatal Outcomes; Fathers of Twins; Doppelgängers and Similarity; Monozygotic Co-Twin Difference in Asymmetric Pigmented Paravenous Chorioretinal Atrophy/In the News: Opposite-Sex Twin Holocaust Survivors; Twin Models at Gucci; Twins With Different Fathers; Reunited Twins Enter Same Convent; Death of a Twin Soldier During Training; Surgical Separation of Conjoined Twins.

Quadruplets are at elevated physical risks at prenatal, perinatal, and postnatal levels, relative to twins. A brief review of this area is followed by discussion of a female quadruplet with three co-quadruplet brothers. Next, several timely twin research reports are examined. The topics include antenatal corticosteroids and twins' neonatal outcomes, the meaning of fatherhood in families with twins, what doppelgängers (look-alikes) reveal about physical and behavioral similarity, and monozygotic (MZ) co-twin discordance for asymmetric pigmented paravenous chorioretinal atrophy. A lawsuit involving alleged cheating on a medical school examination by identical twins is also reviewed. General interest stories cover opposite-sex twin Holocaust survivors, twin models at a Gucci fashion show, twins with different fathers, reunited female twins who entered the same convent, the death of an MZ female twin soldier during training, and the surgical separation of conjoined twins in Brazil.

Heteropaternal twinning: Unique case of opposite-sex twins with different fathers.

A presumably rare, but naturally occurring twinning event is heteropaternal (HP) twinning. HP twinning results from superfecundation, a reproductive process in which offspring share their mothers, but not their fathers. The resulting twins share an average of 25% of their segregating genes, the same proportion as half-siblings. A recently identified case of HP opposite-sex twins was confirmed by DNA analyses available for the twins and for multiple family members. Thus, an exceptional feature of the current report is the inclusion of data for the twins' brothers, sisters, half-siblings, nieces, nephews and cousins, as well as several parent-child pairs. HP twins often go unnoticed so are typically classified as dizygotic (DZ) twins whose genetic overlap is 50%, on average, but varies across traits. As a unique category of non-identical twins, HP twinning is important to acknowledge as it may affect twins' physical resemblance, behavioral similarity, personal identity, family relations and health concerns. While including HP pairs in twin research has been shown to have minimal impact on heritability estimates, it could conceivably affect the outcomes of small-scale studies. Given a lack of consistent and known prevalence, case studies provide valuable knowledge regarding the occurrence of HP twinning. Its implications for forensic science and for twin research are considerable.

Twins Separated at Birth: Across a Country and Around the World/Twin Research: Memorial Tribute to Isaac Blickstein, MD; Infanticide and Sacrifice of Archaic-Aged Twins and Triplets; Prehistoric Twin Burials; Highlights from a Conference on Three Identical Strangers/Media Reports: An Atypical Twin Father; An Actor's Twin Brother; Twin Link to Tulsa, Oklahoma Massacre; Superfetated Twins; Twin Comedians and Script Writers; Indian Twins' Loss to COVID-19.

Every reared-apart monozygotic (MZ) twin pair offers a fresh perspective on human developmental questions. This is true regardless of whether the co-twins were raised in the same country or across the globe. The members of two pairs of separated MZ female twins have recently come to attention. In one case the twins were raised by different families in Argentina; in the other case the twins were raised by different families in Sweden and Vietnam. The perceptions and perspectives of these twins are insightful. The twin research section that follows begins with a tribute to our late esteemed colleague, Dr Isaac Blickstein (1953-2020). Research concerning the infanticide and sacrifice of Archaic-aged twins and triplets and prehistoric twin burials is reviewed next. Highlights from a conference focused on the 2018 film Three Identical Strangers are also included in this portion. The final section of this article includes media reports of an atypical twin father, an actor's twin brother, a twin link to the 1921 Tulsa, Oklahoma massacre, the birth of superfetated twins, twin comedians and script writers and Indian twins' tragic loss to COVID-19.

Terminating Twins: Survival of One/Twin Research Reviews: Twin Discordance for Primordial Dwarfism; Twin Study of Public Service Motivation; Four-Parameter Model for Twin Research; Global Twinning at a Peak; Germline Differences of Monozygotic Twins/In the News: Twins and Dyngus Day; Triplets Born in Austrian Displaced Persons' Camp; Superior, Film About Estranged Identical Twin Sisters; Adopting Own Twins After Surrogacy; Twins and Primordial Dwarfism Revisited.

Selective termination is the term used for the elimination of an abnormal fetus. In contrast, multifetal pregnancy reduction refers to the termination of one or more members of a twin or higher-order multiple birth set, respectively, to reduce the high risks associated with these pregnancies. The procedure can also be used when a serious physical condition is detected prenatally in a member of a multiple birth set. In a minority of cases, selective termination has reduced two healthy fetuses to one when parents wanted just one additional child in the family. In the present article, the perspectives of a surviving twin whose family wished to terminate both healthy fetuses are examined. Next, past and present twin studies of primordial dwarfism, public service motivation, an analytical model, the global twinning rate and germline differences are summarized. The article concludes with a synopsis of twin-related news that covers twins and Dyngus Day, triplets born in an Austrian displaced persons' camp, the film Superior - about estranged identical twin sisters, a couple adopting their own twins after surrogacy and a new case of twins and primordial dwarfism, a condition introduced in the research reviews.