This article looks in detail at a form of kinship that is contingently crafted and mobilized to achieve specific purposes. On the basis of ethnographic material collected among local actors within bodies that regulate kidney transplants in Israel, the objective of this article is to expand the sociolegal definition of fictive kinship. I use transplant relatedness to refer to the set of formal and informal norms that grow out of social and medico-legal practices in the field of kidney donations and sales; however, the form of fictive kinship that appears in this specific field tells us something broader about kinship as it is constructed and performed in legal processes more generally. The configuration of fictive kinship that is examined is the shared history (historia meshoutefet). I argue that in the present case, the shared history alters social and legal deep-seated understandings of kinship and ultimately makes the distinctions between allegedly real and pseudo-kinship collapse.