Ethnic and kinship ties have long been viewed as potential catalysts for favoritism, and hence corruption. In experiments conducted in three countries, we recruit siblings, coethnics and strangers and vary the relationship(s) between the players of a game to observe how kin and ethnic ties influence the willingness of two players to benefit one another at the expense of a third party. We see universal sibling favoritism, but ethnic favoritism, and favoritism toward other in-group members (friends) varies. We argue this may be driven in part by kinship institutions, since favoritism is more common in societies with denser kin networks. (JEL D9, C9, D73, J12).