The goal of this workshop is to move towards a useful conceptualization of kinship for biology in the 21st century. For decades the evolution and cooperation community has been mired in debates about the nature of cooperation and the role of kinship in selection for altruistic behavior. In this workshop we will briefly examine the question of why this debate exists and why it has lasted so long, but then move forward to a new conceptualization of kinship that is useful for the modern questions and problems that cooperation theory deals with. We will take an interdisciplinary approach, drawing from several areas of biology and social sciences to develop a synthesis around what constitutes kinship. Kinship in disciplines outside of evolutionary biology is not defined exclusively by genetic relatedness. For example, historically kinship has been largely defined by rules for passing on property and wealth (i.e., non-genetic inheritance systems). In Anthropology, kin terms used in small scale societies do not strictly map onto relatedness. Moreover, feelings of kinship with other species is widespread across many human societies including modern market-integrated ones. In this workshop we will bring together evolutionary biologists, anthropologists and historians to reconceptualize kinship in the light of not just evolution but also the social sciences.