Considerable  research  has  examined  infants’  reasoning  about  and  evaluations  of  social  agents,  but  two  questions  remain  unanswered: First, do infants organize observed social relations into larger structures, inferring the relationship between t wo social  beings  based  on  their  relations  to  a  third  party?  Second,  how  do  infants  reaso n  about  a  type  of  social  relations  prominent  in  all  societies:  kinship  relations  that  modulate  caregiving?  In  a  series  of  experiments  using  animated  events,  we  ask  whether  9 - ,  11 - ,  and 15 - to 18 - month - old infants expect two babies  who  were comforted by the same caregiver, or two caregivers  who comforted  the same baby, to affiliate with one another. We find that older infants make these inferences in a caregiving context, but n ot in a  different context involving social interactions among adults. Thus, infant s are sensitive to at least one aspect of kinship relations — caregiving — and organize these relations into larger social structures.