This is a major comparative study of early Irish and Welsh kinship. Kinship is a central element in all human societies and was of particular significance in early medieval Ireland and Wales where government institutions were, in general, weak. T. M. Charles-Edwards examines the forms of kinship found in Ireland and Wales at the earliest periods for which documentation is sufficient (the seventh century for Ireland and the twelfth through thirteenth centuries for Wales). His analysis of kinship vocabulary and careful consideration of the available evidence enables him to take the discussion back to earlier periods. This is the first extended scholarly treatment of the topic. It is an intensively researched, erudite, and fascinating study of the interplay of tradition and innovation in the development of kinship from the prehistoric to the medieval period.