Siblings have considerable influence on one another's development throughout childhood, yet most human development research has neglected sibling socialization. Through this volume, we aim to enhance our understanding of how siblings play formative roles in one another's social and emotional development. We examine the mechanisms by which children are influenced by their brothers and sisters, clarify the ways in which these mechanisms of socialization are similar to and different from children's socialization experiences with parents, and consider the conditions under which sibling socialization results in positive versus negative consequences for individual development.

Objective: The purpose was to test a new evidence‐based online preventive intervention designed to help parents improve the sibling relationships of their 4‐ to 8‐year‐old children.Background: Few evidence‐based resources exist to address parents' concerns about fostering positive sibling relationships. To address this need, the emotion‐focused online program placed parents in the role of educator, preparing them to teach their children social and emotional competencies shown in previous research to promote prosocial sibling interaction.Method: Eighty‐six mothers provided assessments of children's sibling relationship quality, child and parent emotion regulation abilities, and coparenting quality prior to and following completion of four online lessons. A randomly assigned wait‐list control group of mothers (n = 49) provided comparable assessments.Results: Repeated measures multivariate analyses of covariance revealed that, following program completion, participants perceived their children to demonstrate greater sibling warmth and less agonism and rivalry. Effects were sustained at 3 months. Mothers also reported increased abilities to regulate their own emotions as well as greater collaboration and support in their coparenting relationship.Conclusion: Results support the effectiveness of the online More Fun with Sisters and Brothers Program for Parents for enabling mothers from diverse international communities to support positive sibling relationships.Implications: Increasing access to evidence‐based tools for strengthening sibling relationships can enable parents to support these vital lifelong bonds.

Parents’ ability to manage intense emotions in the face of conflictual sibling interactions is a significant challenge that has been linked with various child and parent outcomes. With existing instruments focused on raising a single child, we lack validated instruments to assess dimensions of parental emotion regulation in the context of rearing siblings. We tested the factor structure, reliability, divergent and concurrent criterion validity of a new instrument designed to measure parental emotion regulation ( Parental Emotional Regulation in the Sibling Context Questionnaire ) while raising two or more children. Participants, 359 mothers from 35 countries, with two children aged 4- to 8-years, completed the new instrument along with established measures of parental emotion regulation, sibling relationship quality, and children’s emotion regulation. A confirmatory factor analysis supported the utility of the instrument in reliably assessing dimensions of parent emotional regulation (Reactivity and Dysregulation). Evidence for divergent validity stemmed from associations with an established measure of general emotion regulation strategies and evidence for concurrent criterion validity stemmed from associations with children’s sibling relationship quality. Findings have implications for the reliable identification of mothers who are facing emotion regulation difficulties, the design of customized intervention strategies, and the evaluation of prevention and intervention programs.

This systematic review addresses the gap in the literature regarding sibling relationship quality among Latinx families, a topic that has not been comprehensively examined to date. This study aimed to synthesize current research on sibling relationship quality in Latinx families, focusing on the influence of cultural factors, identifying key variables associated with sibling relationship quality, and evaluating the methodological approaches used. This paper is a systematic review based on a recently published evidence and gap map (EGM) that identified and visually presented all published studies investigating sibling relationship quality. Additional inclusion criteria were applied to select articles that specifically examined sibling relationship quality in the United States samples with at least 50% Latinx participants. The review included 12 articles representing 6 distinct studies, revealing significant findings on the roles of familism, simpatía, and gender in shaping sibling dynamics. Results indicated that cultural values such as familism and simpatía positively influence sibling intimacy and warmth, while gender dynamics further moderate these relationships. Methodologically, the articles employed longitudinal and cross-sectional designs, utilizing various quantitative measures. The findings underscore the importance of culturally sensitive approaches in studying sibling relationships and highlight the need for further research to explore these dynamics in diverse Latinx subgroups.