CONTEXT: The association between youths' sexual and reproductive attitudes and behaviors and those of their peers and parents has been documented; however, information on siblings' influence is scarce, especially for developing countries.

METHODS: Data on 1,395 female and 1,242 male survey respondents aged 15–24 from three cities in Côte d'Ivoire were analyzed. Life-table analysis was conducted to examine respondents' probability of remaining sexually inexperienced according to siblings' history of premarital childbearing. Cox multivariate regressions were used to estimate respondents' relative risks of sexual debut by age 17 and by age 24.

RESULTS: At any age between 15 and 24 years, the life-table probability of remaining sexually inexperienced was typically lower among persons who had at least one sibling with a premarital birth than among those who had no such sibling. In general, among those with at least one sibling who had had a premarital birth, the probability was lower if the sibling or siblings and the respondent were of the same gender rather than opposite genders, and the probability was lowest among those who had a brother and a sister with a history of premarital childbearing. In the multivariate analysis for males, having one or more brothers only, or having at least one brother and at least one sister, with a history of premarital childbearing was associated with increased relative risks of being sexually experienced by ages 17 and 24. No such association was found for females.

CONCLUSION: Programs that seek to reduce premarital sexual activity among young people should develop strategies that take into account the potential influence of siblings.