Demographic estimates of sexually diverse co-residential relationships in the United States have traditionally concentrated on the sex composition of couples or the sexual identity of one partner alongside their relationship status. Using population-based dyadic data from the National Couples’ Health and Time Study, which encompasses U.S. co-residential partnered adults aged 20–60, authors provide national estimates of couples’ sexual identity composition.

Findings: According to dyadic reports of sexual identity, 10.94% of couples included a partner who identifies as sexually diverse, more than double the estimate derived from the reported sexual identity of one partner (4.31%). Specifically, 2.44% of couples had both partners reporting a sexually diverse identity, while 8.50% had only one partner doing so. Bisexual-identifying individuals and those with another/multiple sexual identities frequently have partners who identify as heterosexual. In contrast, gay/lesbian and heterosexual-identifying adults often have partners with the same sexual identity. The sociodemographic portrait also revealed notable variations in the sociodemographic characteristics of couples based on their sexual identity composition. Authors argue that capturing couples’ sexual identity composition further elucidates the demography of contemporary U.S. families.