This paper is concerned with exploring how ideas about genes and genetic relationships are rendered meaningful in everyday life. David Morgan’s concept family practices (1996) has significantly shaped sociological inquiries into family lives in recent decades. It represents an important step away from a focus on family as something you ‘are’ to family as something you ‘do’. With a focus on family as a set of activities, it however functions less well to capture more discursive dimensions of family life. Combining a focus on family as practice with an attention to discourse, I concentrate here specifically on ‘genetic thinking’ by which I mean the process through which genetic relationships are rendered meaningful in everyday family living. I draw on original data from a study about families formed through donor conception, and the impact on such conception on family relationships, to show that genetic thinking is a salient part of contemporary family living. The paper explores the everyday, normative assumptions, nuances and understandings about genetic relationships by exploring five dimensions: having a child; everyday family living; family resemblances; traits being ‘passed on’; and family members working out accountability and responsibility within the family. Showing the significance of genetic thinking in family life, I argue for the need for a more sustained sociological debate about the impact of such thinking within contemporary family life. I also argue for the need to develop a sociological gaze more sensitive to the relationship between family as a set of activities and the feelings, imaginations, dreams or claims with which they are entwined.