Anthropological studies of genetic citizenship have focused on illnesses with medically explained etiologies. Such studies tend to trace patients' agency and resistance as they encounter genetic knowledge. By contrast, we explore how genetic knowledge is configured by those suffering from contested illnesses. Through interviews, we examine the claims for health care made by British and New Zealand veterans who in the 1950s took part in nuclear testing in the Pacific. We illustrate how genetic citizenship can be crafted largely without mainstream medical support or state legitimation, showing that participants understood genetics through personal, relational, and affective experiences. These experiences were utilized to build illness narratives in part because they were the best resources available. Veterans also trusted these discourses because they captured experiential knowledge and revealed personal and familial suffering in ways that biomedicine could not.