This article employs the gender-as-relational (GAR) approach to enhance the study of the long-term romantic relationships of sexual and gender minority mid- to later-life adults. The GAR approach states that gender in relationships is shaped by three key factors: own gender, partner gender, and the gendered relational context. This approach emphasizes that the relationship dynamics of men, women, and gender-nonconforming individuals are highly diverse, reflecting that gender is a social construct formed within interactions and institutions. We explicate how GAR can reorganize the study of sexual and gender diversity in three research areas related to aging and relationships—caregiving, marital health benefits, and intimacy—and discuss theory-driven methods appropriate for a GAR research agenda. A GAR framework reorients research by complicating taken-for-granted assumptions about how gender operates in mid- to later-life romantic relationships and queering understandings of aging and romantic relationships to include experiences outside of heteronormative and cisnormative categories.