The birth of an infant sibling is a common occurrence in the lives of
many toddler and preschool children. The current study examined
individual differences in trajectories of young children's behavioral
and emotional adjustment after the birth of a sibling. Growth mixture
modeling (GMM) was conducted with a sample of 241 families expecting
their second child using a longitudinal research design across the first
year after the sibling's birth (prenatal, 1, 4, 8, and 12 months) on
seven syndrome scales of the Child Behavior Checklist. Multiple classes
describing different trajectory patterns of adjustment and adaptation
emerged. There was no evidence of a persistent maladaptive response
indicating children undergo a developmental crisis after the birth of a
sibling. Most children were low on all problem behaviors examined and
showed little change, although some children did experience more
pronounced changes in the borderline or clinical range. There was an
Adjustment and Adaptation Response for aggressive behavior, indicating
that some young children react to stressful life events but adapt
quickly. Data mining procedures uncovered various child, parent, and
family variables that discriminated different trajectory classes.
Children's temperament, coparenting, parental self-effi cacy, and
parent--child attachment relationships were prominent in predicting
children's adjustment after the birth of an infant sibling. When
trajectory classes were used to predict sibling relationship quality at
12 months, children high on aggression, attention problems, and
emotional reactivity engaged in more conflict and less positive
involvement with the infant sibling at the end of the first year.
