J Youth Adolescence DOI 10.1007/s10964-017-0713-5 EMPIRICAL RESEARCH And What About Siblings? A Longitudinal Analysis of Sibling Effects on Youth’s Intergroup Attitudes Katharina Eckstein 1 ● Jan Šerek 2 ● Peter Noack 1 Received: 19 April 2017 / Accepted: 21 June 2017 © Springer Science+Business Media, LLC 2017 Abstract Within the process of political socialization, the family is of particular importance. Apart from parents, however, little is known about the role of other close family members. The present study examined if siblings affect each other’s intergroup attitudes (i.e., intolerance towards immigrants, social dominance orientation). Drawing on a sample of 362 sibling dyads (older siblings: M age = 17.77, 53.6% female; younger siblings: M age = 13.61, 61.3% female), the results showed that older siblings’ intergroup attitudes predicted younger siblings’ attitudes, but this effect was moderated by gender. Specifically, older siblings’ intolerance and social dominance orientation were only found to affect their younger sisters, yet not their younger brothers. Although younger siblings’ intergroup attitudes had no main effect on older siblings, a significant mod- eration by age indicated that younger siblings affected older siblings’ social dominance orientation with increasing age. These moderation effects of age and gender were not mediated by the quality of family relationships. The find- ings also remained the same when parental intergroup attitudes were taken into account. While siblings were generally identified as an important agent of political socialization in youth, the results also highlight the necessity to further examine the mechanism that either facilitate or hinder sibling effects. Keywords Siblings ● Political socialization ● Family ● Youth ● Intergroup attitudes ● Intolerance Introduction Of the many factors that shape young people’s socio- political attitudes, the family deserves particular attention. Home is where most young people first encounter politics and the role of family–primarily of parents–has been well documented within political socialization research (Jennings et al. 2009). One of the most prominent ways in which family affects young people’s socio-political development is the transmission of attitudes and behaviors from parents to their offspring. Accordingly, young people who grow up in a politically active family environment are not only more likely to become active themselves (e.g., Verba et al. 2005), but parents and children also share similar views in various political domains (e.g., Jennings et al. 2009). So far, how- ever, little is known about the role of other family members, such as siblings (Urbatsch 2011). Despite declines in family size throughout the last decades, 75 percent of young people under the age of 18 grow up with at least one sibling in Germany (Statistisches Bundesamt 2011). Comparable rates are also reported for young people in Great Britain, Sweden, or the US (Office for National Statistics 2016; Statistics Sweden 2016; United States Census Bureau 2011). By using a longitudinal multi-informant approach, it was therefore the goal of the present study to examine if siblings affect each other’s intergroup attitudes. We focused on two intergroup attitudes in particular: (1) intolerance towards immigrants and (2) social dominance orientation. While the * Katharina Eckstein katharina.eckstein@uni-jena.de 1 Department of Educational Psychology, Friedrich Schiller University Jena, Humboldtstr. 27, 07743 Jena, Germany 2 Institute for Research on Children, Youth and Family, Masaryk University, Joštova 10, 602 00 Brno, Czech Republic Electronic supplementary material The online version of this article (doi:10.1007/s10964-017-0713-5) contains supplementary material, which is available to authorized users.