Social closeness revisited in monozygotic and dizygotic twin families: Aunt/uncle-niece/nephew relations

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

The commentary delves into the implications of "assortative parenting" and "assortative cross-parenting," as introduced by N. L. Segal, and situates these concepts within the framework of current research. It addresses the joys and complexities of raising twins, highlighting how their concurrent development stages can amplify parental favoritism and heighten the challenge of addressing each twin's unique needs. This interplay provides a rich context to investigate assortative parenting practices. Additionally, this paper contemplates the broader picture of twin studies, particularly how the care of monozygotic twins (who share 100 % of their genes) and dizygotic twins (who share 50 % of their genes, on average) may reveal the intertwined nature of genetics and environment in parenting strategies. It also proposes that twins' interactions with other family members, their spouses, and peers can offer profound insights into the phenomena of phenotypic assortative affiliation, enriching our understanding of close relational bonds.

Brazilian Twin Studies: A Scoping Review

The current study was motivated by an interest in deepening understanding of Brazilian twin research, which is underrepresented internationally, in an effort to rectify this situation. Our aim was threefold: (1) to carry out a comprehensive investigation of Brazilian research on twins according to the area of knowledge; (2) to evaluate the representation of research in the field of psychology in comparison with other areas; (3) to evaluate characteristics of the research that may have contributed to its exclusion from the comprehensive meta-analysis of 50 years of twin research. A scoping review was performed according to PRISMA guidelines. Titles and abstracts were searched up to 2022 in six databases: CAPES, BDLTD, PePSIC, PubMed, Google Scholar, and SciELO, using selected keywords both in Portuguese and in English (e.g., 'twins' and 'Brazil'; 'twinning' and 'Brazil'; 'gemelaridade' [twinning], and 'gêmeos' [twins]). Three hundred and forty publications were included in the review. Approximately half (53.8‰) used the classic twin design to investigate the heritability of several traits, and the other half (46.2%) used other research designs. The scoping review showed that the number of publications doubled approximately every 10 years. Most publications were from the health area, with medicine accounting for approximately half of the studies, followed by psychology, odontology, and biology. We found that the interest in studying twins among Brazilian scientists is increasing over the years and there are reasons to be enthusiastic about the potential impact of this trend in the global scenario.

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.

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.