Drawing on ancient theories of generation, early modern natural philosophers and physicians reflected on family resemblance. We know less about how ordinary people perceived it. This chapter offers some insights by reconstructing the place of the linked notions of resemblance and dissimilarity in the old regime. How traits were understood to pass down the generations had social and political implications, as tracts on the origin of nobility, medical advice for begetting the desired children and paternity disputes reveal. Resemblance was framed in physical, moral and intellectual terms. Intersecting with discussions of the plasticity of nature and free will, why children did or did not resemble their parents encapsulated broader anxieties about individual and family identities, social mobility and challenges to traditional views: in the unpredictable process of generation, noble traits could appear unexpectedly. In the law courts, resemblance competed with other criteria, but informed testimonies and decisions. Though focusing on the seventeenth century, the chapter also sketches later developments, when the competition between theories of generation intensified and sons rebelled against fathers. Central to a cultural history of heredity, family resemblance emerges as the hinge connecting reflections on generation as a natural process and the changing relationships between generations.