In recent years, the empirical literature on cross-national unions—marriages between migrants and members of the majority population—has experienced a shift in focus, with an increasing number of studies examining assortative mating patterns within these unions. This shift marks a significant development, indicating that the classic assimilation theory is no longer considered the sole explanation for cross-national unions. However, the move from analyzing different immigrant groups’ propensity to intermarry toward examining the characteristics of both partners and their assortative mating patterns lacks sufficient theoretical grounding. Drawing on recent empirical studies and the classic status-caste exchange theory, I propose a new theoretical perspective on these unions. Specifically, I introduce a non-exhaustive list of four forms of capital that can be exchanged in the marriage market: economic capital, cultural capital, physical capital and locational capital. I propose that global inequalities lead to an exchange of physical capital for locational capital, or youth for residence, which in turn influences marriage patterns and assortative mating dynamics.