In thirteenth- and fourteenth-century Europe, kinship rules dominated the lives of laymen and laywomen. They determined whom they might marry [decided in the canon law courts] and they determined from whom they might inherit [decided in the common law courts]. This book seeks to uncover the association between the two, exploring the ways in which the two legal systems shared ideas about family relationship, where the one jurisdiction - the common law - was concerned about ties of consanguinity and where the other - canon law - was concerned to add to the kinship mix of affinity. It also demonstrates how the theories of kinship were practically applied in the courtrooms of medieval England.