Why can cross-cousin terminology be connected to marriage rules?

In anthropology, the connection between cross-cousin terminology and marriage rules is rooted in how societies categorize kin to define eligible and ineligible partners.12

Many societies that distinguish between cross-cousins (children of a father’s sister or mother’s brother) and parallel cousins (children of a mother’s sister or father’s brother) use these categories to regulate marriage. In such systems, parallel cousins are often classified as siblings, making marriage between them subject to incest taboos. Conversely, because cross-cousins are categorized as being outside of one's own lineage, they are frequently viewed as ideal or even obligatory marriage partners.12

This terminological distinction serves as a structural device to facilitate exogamy and strengthen alliances between different clans. French anthropologist Claude Lévi-Strauss further developed this through alliance theory, which examines how these kinship categories and marriage rules function to create social order and intergroup bonds. While these terminologies provide a framework for social organization, actual marriage practices remain influenced by local factors such as inheritance and residence patterns.1234