Birth Order and Family Size of UK Biobank Subjects Identified as Asexual, Bisexual, Heterosexual, or Homosexual According to Self-Reported Sexual Histories.

This study used a recently developed statistical technique to investigate the relations between various elements of a subject's family background and the odds of that subject reporting a sexual history indicative of a minority sexual orientation. The subjects were 78,983 men and 92,150 women who completed relevant questionnaire items in the UK Biobank, a large-scale biomedical database of volunteers aged 40-69 years. The men were divided into three sexual minority groups-homosexual, bisexual, and asexual-and a comparison group of heterosexual men.

Are Sibship Characteristics Predictive of Same Sex Marriage? An Examination of Fraternal Birth Order and Female Fecundity Effects in Population-level Administrative Data from the Netherlands.

Despite historical increases in the number of individuals engaging in same-sex relations and entering same-sex unions, the causes of sexual orientation remain an open question. Two biological processes that have received some degree of empirical validation are the fraternal birth-order effect (FBOE) and the female-fecundity effect (FFE). Respectively, these processes posit that having a greater number of older brothers and being part of larger sibships independently increase the odds of male homosexuality.

Academic Achievement of Children in Same- and Different-Sex-Parented Families: A Population-Level Analysis of Linked Administrative Data From the Netherlands.

Although numerous studies have examined how children raised in same-sex-parented families fare relative to children in different-sex-parented families, this body of work suffers from major methodological shortcomings. By leveraging linked administrative data from several population registers from the Netherlands covering the 2006-2018 period (n = 1,454,577), we overcome most methodological limitations affecting earlier research. The unique features of the data include complete population coverage, reliable identification of same-sex-parented families, a large number of children in same-sex-parented families (n = 3,006), multiple objective and verifiable educational outcomes, and detailed measures of family dynamics over children's entire life courses.