We analysed differences in conservative values between firstborn and secondborn siblings, in the context of Sulloway’s (1996) idea that firstborns favour the status quo more than secondborns do. Using multilevel analysis to predict siblings’ conservatism, we tested two hypotheses from Sulloway’s theory: (a) firstborns are more conservative than are secondborns; and (b) firstborns internalize their parents’ conservative values stronger than secondborns do, independent from the degree of their parents’ conservatism. Ninety-six Italian families (composed of both parents, the firstborn and the secondborn, total N = 384) filled out the Portrait Values Questionnaire (Schwartz et al., 2001). Results supported Sulloway’s first, but not his second prediction: Birth order fostered children’s conservatism directly, but not in interaction with parents’ conservatism. Implications of the results for the children’s socialization and their possible developments are discussed.