In this paper, stochastic modeling of the cross-correlation of small-scale fading (SSF) is performed for co-existing propagation channels based on measurement data collected using the relay-Band-Exploration-and-Channel-Sounder (rBECS) systems in urban areas, Korea. We define six geometrical parameters which are considered as variables in the cross-correlation models proposed. These parameters characterize the geographic properties of a three-node co-operative relay system that consists of a base station, a relay station and a mobile station. The sensitivity of the distribution of SSF cross-correlation coefficients with respect to the proposed variables is assessed. Three of them are identified as sensible variables for modeling.