Identification of the product platform is n key step in designing a family of products. This article presents a methodology for selecting the product platform using information obtained from the individual optimization of the product variants. Under the assumption that the product variety requires only mild design changes, the authors derive a sharing penalty vector (SPV) by taking into consideration individual optimal designs and sensitivities of functional requirements. Commonality decisions are based on SPY values and the product family is designed optimally with respect to the chosen platform. An automotive body structure problem is used to demonstrate the proposed methodology. Variants are defined by changing the functional requirements they need to satisfy and/or the geometry of the associated finite element models