Hybrid aircraft are a necessary step in the energy transition towards sustainable aviation, given current limitations in battery technology. However, hybrid systems face significant economic and technological hurdles of their own. This study investigates whether designing hybrid-electric aircraft as part of a family—with shared components and design commonality—can offset economic drawbacks while maintaining environmental benefits. A novel methodology was developed and validated against existing literature, integrating economic and climate models within a hybrid aircraft family design framework. This approach facilitates aircraft family design by strategically constraining design freedom at the subsystem level, introduces a refined calculation of commonality indices, and incorporates these indices into a bespoke economic evaluation framework specifically tailored for commercial hybrid aircraft. Results from a parametric case study demonstrate that increased commonality yields drastic improvements in economic feasibility —on the order of billions of dollars—, while environmental performance varies by less than5%across design families with differing levels of commonality. These findings underscore the critical role of commonality in determining program viability, an effect not previously quantified for hybrid systems. Additionally, family design trends influence program value and emissions in nuanced ways. This work provides guidance for optimizing hybrid aircraft family designs and highlights opportunities for further research in sustainable and economically viable aviation.