Considerable research has examined infants' understanding and evaluations of social agents, but two questions remain unanswered: First, do infants organize observed social relations into larger structures, inferring the relationship between two social beings based on their relations to a third party? Second, how do infants reason about a type of social relation prominent in all societies: the caregiving relation between parents and their babies? In a series of experiments using animated events, we ask whether 15- to 18-month-old infants infer that two babies who were comforted by the same adult, or two adults who comforted the same baby, will affiliate with one another. We find that infants make both of these inferences, but they make no comparable inferences when presented with the same visible events with voices that specify a peer context, in which one adult responds to another laughing adult. Thus, infants are sensitive to at least one aspect of caregiving and organize relations between infants and adults into larger social structures. (C) 2016 Elsevier B.V. All rights reserved.