Evidence That the Presence of a Half‐Sibling Negatively Impacts a Child's Personal Development

. This paper examines the relationship between a child's family structure and his or her development. While most prior research in this area has defined a child's family structure according to his or her relationship to adults in the household, this study examines the relationship of the child to not only adults but also other children in the household. We provide evidence that half‐siblings brought into the household from previous relationships affect the well‐being of children born into a subsequent marriage who live with both of their biological parents. Stepchildren and children living with both biological parents exhibited more behavior problems and scored worse on reading achievement tests when half‐siblings were present. In contrast, stepchildren living without half‐siblings in the home fared no worse than biological children without half‐siblings. These results not only highlight a previously overlooked at‐risk group (children living with half‐siblings brought into the household from a parent's prior relationship), but they also illustrate the potential ramifications of classifying children into family structures based on their individual relationship with the householders, rather than based on the family types. The authors illustrate the relevance of these findings to current policy‐making decisions regarding marriage promotion policies and child support legislation.