Change in maternal perception of sibling negativity: within- and between-family influences.

Change in maternal report of sibling negativity was investigated in 313 sibling dyads from 171 families taking part in a longitudinal, general population survey in the United Kingdom. The inclusion of multiple dyads per family allowed for the emergence of 3 novel elements for sibling research: an examination of within-family similarity on sibling relationship quality, modeling within-family similarity as a function of the shared environment and the differentiation of family-wide and dyad-specific predictors. Moderate similarity on sibling negativity was found across different sibling dyads and similarity was higher in 2 versus lone-parent families. Maternal negativity, genetic relatedness, age of the oldest child in the dyad, and the interaction between lone-parent status and maternal differential treatment were found to predict change in sibling negativity.