Parental differential treatment is associated with higher levels of psychopathology symptoms in children. Both higher overall levels of differential treatment (absolute/magnitude of differential treatment) and consistently favoring one child over another (relative differential treatment) are associated with risk in children. This study enhances understanding of parental differential treatment using a genetically informed twin design that clarifies child- and parent-driven effects. Participants included 632 twin pairs (Mage = 7.6 years, SD = 0.94; 96% White, 44% Rural) and parents. Parental differential treatment was assessed using an observed card game interaction and reports from mothers, fathers, and children. Twin modeling indicated heritable influences on parental hostility (h2 = .34 for females, .06 for males) and intrusiveness (h2 = .51 across the sample), suggesting that children’s heritable traits elicit parenting. Observed intrusiveness differences predicted ADHD. Absolute and relative differences in maternal discipline predicted externalizing, internalizing, and ADHD symptoms, with a similar but less strong pattern for paternal discipline. However, absolute differences in paternal affection and paternal partiality proved especially important for children’s psychopathology. Findings show children’s behavior can elicit maladaptive differences in parenting, informing interventions.

This study examined the link between sibling relationships and children's social adjustment by comparing twin siblings and siblings with different ages (singleton siblings), and clarified the role of reciprocity in sibling relationships on children's social development. Mothers of 58 monozygotic twin pairs, 48 dizygotic twin pairs, and 86 singleton sibling pairs reported their children's sibling relationships and social adjustment. This study showed that the effects of sibling relationships on the prosocial behaviors and conduct problems of each child are stronger for twins than for singleton siblings. Moreover, positivity toward one's sibling increased peer problems only among monozygotic twins. The opposite tendency was present among dizygotic twins and singleton siblings. This study suggests the importance for children's social development of having many interactions with siblings and establishing reciprocity in sibling relationships. Moreover, our results suggest that the quality of sibling relationships among monozygotic twins may be different from those among dizygotic twins and singleton siblings.

The aim of this article is to analyse 20 Finnish working carers' perceptions of their sibling relations and the sharing of the responsibility for parental care. The main focus is on the interviewees' rationales for the participation or non-participation of their siblings in the parents' care. Almost all the interviewed carers stated that the division of care responsibilities is unequal and that they are the primary carers, but the majority did not convey any clear intention to try to persuade their siblings to increase their participation in parental care. In many cases, the siblings were described either as entirely absent or as providing occasional backup, but some interviewees reported that caring for the parent(s) was shared with their other siblings. Consequently, three participation patterns were identified: ‘absence’, ‘backup’ and ‘togetherness’. All the interviewees offered rationales for the unequal division of care tasks and responsibilities among the siblings. The discussion focuses on these rationales and their variations by participation patterns, and considers the similarity of the findings to those from previous American and British studies. The study concludes that social-care services should take the primary carer's siblings into consideration, although not always as a ‘resource’. It should not be taken for granted or assumed that the primary care-giver receives help from her or his siblings, even if their relationship is otherwise close and unproblematic.