The New Family Structures Study (NFSS) is a social-science data-collection project that fielded a survey to a large, random sample of American young adults (ages 18–39) who were raised in different types of family arrangements. In this debut article of the NFSS, I compare how the young-adult children of a parent who has had a same-sex romantic relationship fare on 40 different social, emotional, and relational outcome variables when compared with six other family-of-origin types. The results reveal numerous, consistent differences, especially between the children of women who have had a lesbian relationship and those with still-married (heterosexual) biological parents. The results are typically robust in multivariate contexts as well, suggesting far greater diversity in lesbian-parent household experiences than convenience-sample studies of lesbian families have revealed. The NFSS proves to be an illuminating, versatile dataset that can assist family scholars in understanding the long reach of family structure and transitions.