Tuned mass damper inerter (TMDI) is commonly reported to be a lightweight tunable device that can significantly reduce buildings’ seismic response. However, the backward action produced by the inerter and returned to the building in conventional TMDIs may either reduce the device performance or limit the inerter potential. This study proposes and investigates a novel control scheme using large physical mass ratios generated by lightweight inerters. Hence, a double mass tuned damper inerter (DMTDI) is formulated. The proposed control scheme consists of two TMDs placed at the roof of the building and connected via an inerter. Thus, the inerter backward action is transmitted to the secondary mass instead of the building. Both TMDI and DMTDI parameters are optimized using a genetic algorithm (GA). The top floor displacement transfer function’s H2- norm is considered as the objective function for minimization. The optimally tuned devices are then tested under one hundred (100) near and far-field ground motions. The results obtained show a significant response improvement in peak displacement, acceleration, and base shear. The structure energy is also investigated; the lowest energy response in the studied structure is observed while using the proposed DMTDI scheme.