Maloney and Dal Martello [Maloney, L.T., Dal Martello, M.F. (2006). Kin recognition and the perceived facial similarity of children. Journal of Vision, 6(10), 1047-1056. http://www.journalofvision.org/6/10/4/] reported that similarity ratings of pairs of related and unrelated children were almost perfect predictors of the probability that those children were judged as being siblings by a second group of observers. Surprisingly, similarity ratings were poor predictors of whether a pair was same-sex or opposite-sex, suggesting that people ignore cues that are uninformative about kinship when making similarity judgments of faces. Using adult sibling faces, we find that similarity ratings for same-sex pairs were significantly higher than for opposite-sex pairs, suggesting that similarity judgments of adult faces are not entirely synonymous with kinship judgments.