Increasing prevalence of ageing stepfamilies and stepchildren's potential to act as a source of support for older parents has prompted research about intergenerational cohesion in steprelationships. Our purpose is to investigate emotional closeness in biological and step-relationships in ageing stepfamilies, and the explanations older parents and adult children give to such differences. We study emotional closeness in parent-child relationships among Swedish older parents (aged 66-79) who have raised both biological and stepchildren, and adult children (aged 31-57) who were raised by both biological and stepparents. Qualitative family history interviews (n = 24) including hierarchical maps of long-term family relationships were collected and analyzed. Results show biological relationships to be rated as emotionally closer than step-relationships, by both parents and children. This gap in closeness is explained by the informants in terms of (a) personal characteristics, (b) social circumstances and (c) the importance of blood. Both children and parents use the first two explanations, but there is a clear generational difference concerning the perceived importance of blood. While older parents deemphasize the importance of blood for emotional closeness, adult children emphasize it. The study contributes to ageing stepfamily research by including stepfamily members' own perspectives on emotional closeness.