The master structure of product families, as a configuration network, is a collection of a variety of modular components and their configuration relationships. In the forming processes of the master structure of product families, various modularity types reveal complex dynamic behaviors with strong impacts on the connectivity of networks. The connectivity of the directed configuration network of realistic industrial steam turbines is investigated and found to be heterogeneous. The heterogeneity of configuration networks results from the reusability difference of components based on the copy mechanism, and the preferential and random attachment mechanisms of inputs and outputs of directed edges. Finally, an evolving model is established to characterize the growing process of the master structure of product families.