Parental Differential Treatment and Sibling Relationship Quality: A Longitudinal Study

Parental differential treatment (PDT) is an important aspect of children’s unique experiences within the family environment, with well-established links to lower-quality sibling relationships. Existing literature often assumes that PDT fosters anger and rivalry. However, the reverse association may also be true, with poor sibling relationships disrupting parental attitudes and behaviors that exacerbate differential parenting. The directionality of the observed relationship is important to address for understanding the internal workings of family dynamics and the particular role of sibling relationships. Thus, the current study explored directional associations between PDT and sibling relationship quality using a longitudinal, repeated-measures design. Data were from an international sample of caregivers ( n = 497; 43.46% female) with two children each ( n = 994) between the ages of 5–17. Random-intercept cross-lagged panel models examined the longitudinal associations between PDT and sibling relationship quality, while partitioning between- and within-families variance. Irrespective of time, findings suggested that higher overall PDT and differential negativity specifically were related to poorer-quality sibling relationships between families. Furthermore, within families, more differential negativity predicted better sibling relationship quality at a later time point, and poorer sibling relationship quality led to subsequent decreases in differential negativity. Interpreted through the lens of homeostatic effects and feedback loops within family systems, the findings illustrate the dynamic ways in which families achieve stability, in addition to underscoring sibling relationship quality as a potential protective factor against differential parenting.