Does sibling differentiation promote relational harmony or discord? Evidence from a longitudinal dyadic study

Sibling differentiation (or deidentification) is theoretically posited as a mechanism that reduces competition and comparison between siblings and thus fosters sibling harmony (i.e., more positivity and less negativity). Empirical research, however, reveals inconsistent findings regarding the links between sibling differentiation and youths’ sibling relationship qualities. The present study utilized a longitudinal dyadic design to investigate whether sibling differentiation promoted relational harmony or discord over time and to identify the reciprocal longitudinal linkages between older and younger siblings’ perceptions of differentiating from each other. Two waves of survey data were collected from 682 families (older siblings: 51% female, M = 15.67 years; younger siblings: 48% female, M = 13.14 years; and one parent: 85% mothers, M = 45 .15 years at Time 1) in five Midwestern states in the U.S. Results suggested that adolescents who tried to differentiate more from their siblings perceived their relationships more negatively at follow-up. These findings held for both older and younger siblings and are consistent with prior cross-sectional research, but inconsistent with deidentification theory. Additionally, older and younger adolescent siblings’ differentiation efforts were mutually related over time, especially among siblings from same-gender dyads. The discussion focuses on the relational impact of sibling differentiation and the reciprocal influences of differentiation between consecutively-born siblings during adolescence.