Why and how economists have historically studied families is not well understood, neither by those in the discipline, nor by scholars studying families in neighbouring fields like sociology, anthropology, and philosophy. This lack derives from a mistaken view that family economics began in the 1960s when price theory was applied to family behaviour. It is also due to the narrowing of economics from the 1940s in the US, when social reform and advocacy work shifted to the discipline’s periphery. Affirming a contemporary need for gender-inclusive language, while using terms that access historical understandings, the book’s first goal is to show that economists developed methodologies for studying families as a function of how they conceptualised family poverty in different periods. Four historical phases are identified, with economists studying nineteenth-century deficits in family labour productivity in Britain and Europe, inadequacies in low-income family consumption in interwar America, underinvestment in human capital by a post-war ‘underclass’, and gendered injustices in resource distribution experienced by lone mothers, by women and girls in poor global South families, and by queer families. The book’s second goal is to show how family economists prioritised some social problems over others, allowing certain injustices to remain uncontested.