A comparison of partner resemblance trends across putative same-sex and opposite-sex couples in the UK biobank

The study of partner resemblance has widespread implications in the social and natural sciences. To date, the vast majority of such research has focused on opposite-sex couples. This study compared patterns of partner correlations ("assortment") across 66 traits in the UK Biobank (UKB) in 89,628 female-male (FM), 236 female-female (FF), and 216 male-male (MM) putative couples. The average FF, MM, and FM correlations were positive (indicating similarity rather than dissimilarity), though both same-sex partner types yielded significant correlations for only a minority of traits at the Bonferroni-corrected level. FM pairs showed more positive assortment (p_unadjusted<2e-16) than did MM or FF pairs for year of birth and number of children. Much existing same-sex partner correlation research has reported less similarity for age in MM pairs compared to opposite-sex pairs, while some (though not all) of the literature has reported lower similarity for age in FF pairs than in FM pairs. Expanding knowledge about same-sex assortment can contribute to family-based genetic designs and relationship psychology research in addition to diversifying couple-centered treatment modalities. Finally, this research can help to identify how couple dynamics and shared systemic factors potentially relate to ageing-related outcomes, behavior change, and healthcare needs in the LGBT community.