Legislative changes in recent years have emphasised the continuing tie with the biological parent after divorce. This paper consequently considers both legal and everyday discourses concerning the position of step-parents, with reference to any rights or responsibilities they might have towards their step-children. We suggest that two main themes can be discerned: that children need (biological) parents, and that children need (social) families. In intact nuclear families these two themes are mutually reinforcing, but in step-families they are in considerable tension. While legal discourses have increasingly stressed the former theme, evidence from an in-depth English study of resident and non-resident parents and step-parents suggests far more complexity and ambivalence in everyday understandings of these issues. Social class is shown to be strikingly related to the differential use of these two moral discourses, while gender and parental status are also important features at times. Children's own needs and wishes may also be invoked in particular ways, while children themselves may or may not experience this as beneficial. We suggest that recent legislative changes may reflect 'top-down', political and professional concerns, driven by the demands of particular sections of the middle class, and be significantly out of 'step' with the everyday understandings of people directly living in these situations.