How does exchange marriage connect two families?

Exchange marriage connects two families by establishing a reciprocal and symmetric alliance through the systematic trade of spouses. In this arrangement, when a daughter from one group (Group A) marries a son from another (Group B), a corresponding marriage is arranged between a daughter from Group B and a son from Group A.1

This practice is most prevalent in societies with patrilineal descent and patrilocal residence, where it serves to maintain balance between the involved groups. A traditional ideal often involves a brother and sister from one family marrying a sister and brother from another. When these reciprocal exchanges are sustained across subsequent generations, the system is referred to as cross-cousin marriage. By formalizing these ties, the practice creates a lasting social and kinship bond between the two families.123