Since the start of the twenty-first century, the literature on same-sex couple relationships and families headed by single parents who identify as lesbian or gay has grown exponentially, and research published in the past 10 to 15 years tackles many new questions about sexual minority families. This review concentrates on four topics that have dominated the sociological arena: who counts as family and how/whether changing definitions of family incorporate households formed by lesbian, gay, bisexual, and transgender (LGBT) people; the biological, social, and legal obstacles that influence family formation for this population; the outcomes for youth raised with lesbian or gay parents; and family dynamics , relationship quality, and relationship dissolution in same-sex couple and transgender partner households. We conclude with future directions for the sociological study of LGBT sexuality and families.