We deploy 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 within relationships is shaped by three key factors: own gender, partner's gender, and the gendered relational context. This approach highlights that the relationship dynamics of men, women, and gender nonconforming people 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 within mid- to later-life romantic relationships and queering understandings of aging and romantic relationships to include experiences outside of heteronormative and cisnormative categories.