In two comparative studies, both conducted in China and in the Netherlands, we investigated the effect of an asymmetric relationship on lay third parties' side-taking preference in an interpersonal dispute. The first study shows that a perceived close relationship with one of the disputants motivates both Chinese and Dutch lay third parties to side with that disputant. The second study complicates the interpersonal relationship and side-taking link by taking account of contrasting information (either legitimacy or negative sanctions) about the other disputant and cultural dimensions (horizontal and vertical individualism-collectivism). The results suggest that contrasting legitimacy information has a decisive effect on lay third parties' side-taking preference, especially among Dutch lay third parties who highly value vertical individualism. In addition to legitimacy criteria, Chinese lay third parties, whether individualistic or collectivistic oriented, seem to also consider interpersonal relationship and sanction information when making their side-taking decision.