In this article, Turkish mothers’ perspectives on sibling relationships are described and analyzed on the basis of 15 qualitative interviews. It is surprising that sibling relationships have received little attention in cultural psychological or sociological research for decades, while other social relationships—such as parent–child relationships, (marital) partner relationships, peer relationships, or hierarchical relationships (e.g., superior–subordinate)—were often studied. The two main goals of the present study are first, to examine Turkish mothers’ ethnotheories of sibling relationships between their own offspring and second, to analyze these parental ethnotheories through the lenses of the cultural psychological and sociological concepts of collectivism/individualism and interdependent/independent self-concepts. The interview data for this empirical study was derived from a larger project which focuses on parental ethnotheories more broadly. Problem-centered interview method was used. Eleven of the interviews took place via a digital platform due to the COVID-19 pandemic, while four of the interviews were conducted face-to-face just before pandemic’s onset. The Turkish mothers interviewed were from Istanbul and Sinop, a small Turkish city on the coast of the Black Sea. The data was interpreted using the documentary method and relational hermeneutical analysis. The article examines and discusses three topics of sibling relationships, namely hierarchical/equal sibling roles based on birth order, solidarity/sharing, and conflict. We show that all of the mothers interviewed place a high value on connectedness between siblings. With regard to the hierarchical or egalitarian distribution of roles, some of the interviewees differ.