The Sibling Interaction and Behavior Study (SIBS) is a population-based study of 617 families (409 adoptive, 208 non-adoptive) each with an adolescent sibling pair and at least one but typically two rearing parents. Adoptive families were systematically ascertained from infant placements made by three private Minnesota adoption agencies. Reflective of changes in adoption practices over the past 20 years, these agencies minimally screen prospective parents. That is, they must demonstrate a commitment to raising a child, meet a modest minimum income level, and undergo a criminal check, although a criminal record does not preclude placement. Non-adoptive families were ascertained through Minnesota birth records and selected to have a pair of siblings of comparable age and gender to the adoptive sibling pairs. All families were required to live within driving distance of the University of Minnesota
