Gender diversity and the twin relationship: "If I'm feeling this way, shouldn't my twin be feeling this way too?"

Background: Twin studies have been pivotal in advancing knowledge of genetic influence on gender diversity. However, the extent to which the unique dynamics of the twin relationship may also influence gender formation, and potentially distinguish twins from the broader trans community, remains unknown. Method: This study recruited 11 young people from the Royal Children's Hospital Gender Service in Melbourne, Australia, and conducted semi-structured interviews, investigating the interplay between gender diversity and the twin relationship. The interviews were analyzed using Inductive Content Analysis with three coders. Results: The results found that for most trans participants, their twin relationship either served as a source of support or had no notable impact on their gender journey. Similarly, cisgender participants with a trans co-twin did not report any significant consideration or questioning of their own gender identity prompted by their twin's coming out. In most cases, the twin relationship was maintained or strengthened after the coming out process, particularly in the long term. Conclusion: Overall, the twin relationship likely functions similarly to other close relationships (i.e. parents, non-twin siblings), notably the potential to provide affirming support, rather than contributing to a twin-specific experience. However, further research is required to explore these dynamics in greater depth.