How do individuals come to hold certain beliefs about meritocracy, individualism, and redistribution? Several sociodemographic factors are regularly used to understand variation in these beliefs, but other predictors remain untested. Meanwhile, scholars studying family dynamics are increasingly turning their attention toward the long-term social effects of distinct family features. One facet of this work focuses on the social role of siblings. We investigate the relationship at the intersection of these literatures. How does growing up with (more) siblings influence one’s inequality beliefs? Do siblings promote collectivism or might these same relationships foster competition and individualism? Could trust be the mechanism connecting sibship size with inequality beliefs? Or, do sibling effects reflect a broader promotion of conservative thinking in larger families? We investigate these questions using data from the General Social Survey from 1984 to 2018. Our results indicate that siblings are associated with more conservative meritocracy beliefs. On the other hand, we find limited evidence of siblings influencing attitudes toward redistribution.