Product family design allows innovative companies to create customized product roadmaps, to manage designers and component partners, and to develop the next generation of products based on platform strategies. In product family design, problems for determining a design strategy or the degree of commonality for a platform can be considered as a multidisciplinary optimization problem with respect to design variables, production cost, company's revenue, and customers' satisfaction. In this paper, we investigate strategic module-based platform design to identify an optimal platform strategy in a product family. The objective of this paper is to introduce a multi-objective particle swarm optimization (MOPSO) approach to select the best platform design strategy from a set of Pareto-optimal solutions based on commonality and design variation within the product family. We describe modifications to apply the proposed MOPSO to the multi-objective problem of product family design and allow designers to evaluate varying levels of platform strategies. To demonstrate the effectiveness of the proposed approach, we use a case study involving a family of General Aviation Aircraft. The limitations of the approach and future work are also discussed.