A product family is a set of products that are derived from common sets of parts, interfaces, and processes, known as the product platform. To reduce development time and procurement and operating costs of product platform-based variants, the product platform can be designed after consideration of several characteristics, such as modularity, flexibility, sustainability, and complexity. In this paper, the product platform is viewed from the perspective of system architecting. The architectural complexities of both the platform and its variants, which together constitute a product family, can be quantitatively assessed using a specifically tailored metric. This will aid system architects in designing product platforms and resulting product variants with an emphasis on reducing complexity. Architectural complexity management is demonstrated through a case study of a train bogie platform.