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Recent studies suggest this effect might also apply to bisexual and asexual individuals who have been overlooked by previous scholarship. In this study, I explored associations of the FBOE and other sibship effects with minority sexual orientation in an online collected sample of heterosexual (\n                    <jats:italic>n<\/jats:italic>\n                    \u2009=\u20091174), bisexual (\n                    <jats:italic>n<\/jats:italic>\n                    \u2009=\u2009432), and asexual (\n                    <jats:italic>n<\/jats:italic>\n                    \u2009=\u200990) men and women from Czechia and Slovakia. Results of the binary logistic regression indicated the FBOE in bisexual men (\n                    <jats:italic>OR<\/jats:italic>\n                    \u2009=\u20091.66) but not in other sexual minority groups. There were no significant differences in other sibship characteristics between sexual minority and heterosexual individuals, although other non-heterosexual study groups showed a non-significant FBOE of a magnitude similar to bisexual men. This study contributes to the limited literature on understudied bisexual and asexual populations and indicates that male bisexuality might share a common biodevelopmental origin with male and possibly also female homosexuality.\n                  <\/jats:p>","DOI":"10.1007\/s10508-026-03536-9","type":"journal-article","created":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T18:00:31Z","timestamp":1790100031000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Fraternal Birth Order Effect and Other Sibship Effects in Bisexual and Asexual Men and Women"],"prefix":"10.1007","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1980-3607","authenticated-orcid":false,"given":"Jakub","family":"Fo\u0159t","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2026,9,22]]},"reference":[{"issue":"6","key":"3536_CR1","doi-asserted-by":"publisher","first-page":"671","DOI":"10.1080\/00224499.2021.1974330","volume":"59","author":"C Ablaza","year":"2022","unstructured":"Ablaza, C., Kab\u00e1tek, J., & Perales, F. 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