The 'success' of a conversion depends on the group into which the convert is introduced. This study in early Christian ecclesiology from the perspective of house and family is guided by this sociological theory. Converts often met with problems in relation to their family. They joined a fellowship which conceived of itself as a family of brothers and sisters. It is the aim of this investigation to present the potential of the Christian fellowship to take the role of a new family in relation to its converts. This is done by means of historical material and cross-cultural comparisons. The relevance of the material for present-day churches and mission is considered.