Within the formalism of the one-sublattice modified quasichemical model an equation for the computation of pair fraction distributions is derived considering distinct model modifications reported in the literature. For generalization an equation system is presented to determine pair fraction distributions of multicomponent solutions. Consistency of the derived equation with the analogous relationship of former versions of the modified quasichemical model is demonstrated. The derived equation is applied to the Cu-Fe-S liquid solution and its binary subsystems. Pair fraction distributions calculated exemplarily at 1200 °C (1473 K) are used to interpret recently reported predictions of the high-temperature Cu-Fe-S system.