The objective of this study was to explore parents' communication about risk with siblings of children affected by an inherited genetic condition, and to ascertain what level of support, if any, is required from health professionals. Semi-structured interviews were conducted with affected and unaffected children and their parents. Families were affected by one of six genetic conditions representing different patterns of inheritance and variations in age of onset, life expectancy and impact on families. Interviews were analysed using constructivist grounded theory and informed by models which focused on three different aspects of family communication. Interviews with 33 families showed that siblings' information and support needs go largely unrecognized by health professionals and sometimes by parents. Some siblings were actively informed about the genetic condition by parents, others were left to find out and assimilate information by themselves. Siblings were given information about the current symptoms and management of the genetic condition but were less likely to know about its hereditary nature and their own potential risk. When siblings were fully informed about the condition and included in family discussion, they had a better understanding of their role within their family, and family relationships were reported to be more harmonious. The information and support needs of siblings can be overlooked. Parents with the responsibility for caring for a child affected by a genetic condition may require support from health professionals to understand and respond to their unaffected children's need for more information about the genetic condition and its implications for the children's own future health and reproductive decision-making.