This chapter develops Hsu’s Secondary Group Hypothesis, which explores how individuals form social ties beyond the kinshipsystem and how dominant kinship relationships shape the formation of non-kinship organizations. The hypothesis posits that ifprimary groups—centered around kinship—fail to fulfill an individual's psychosocial homeostasis, individuals will seek out orcreate secondary groups to restore balance. Drawing on cross-cultural comparisons among Chinese, American, and Hindusocieties, Hsu identifies the lineage, the association, and the caste as the dominant secondary groups, each rooted in distinctdominant kinship relationships: father–son, husband–wife, and mother–son, respectively. The chapter further elaborates threeorganizing principles—kinship solidarity, contractual solidarity, and hierarchic solidarity—which persist across different typesof secondary organizations and reflect the original affective structure learned within primary groups. These principles are notonly structural but also psychological and cultural in nature, shaping behavioral patterns even in the absence of formal kinshipties. The chapter concludes by applying this framework to explain the long-term features of Chinese political culture, Americanassociationism, and Hindu social hierarchy, while also offering insights into Japan’s modernization through the iemoto systemas a dominant secondary group.