This study addresses the critical water-energy nexus in water-scarce regions by proposing an integrated multiobjective optimization model for a holistic hybrid renewable energy system (HRES) that co-generates electricity, desalinated water, and hydrogen. Using Doha, Qatar, as a case study, a system comprising photovoltaics, wind turbines, batteries, and green hydrogen technologies was optimized against eight conflicting sustainability objectives using the Multi-Objective Grey Wolf Optimizer (MOGWO) algorithm. A key methodological innovation is the development of a transparent cost allocation framework based on primary energy usage, enabling precise apportionment of shared costs among the three outputs. The optimized system results in a Levelized Cost of Energy (LCOE) of $0.068/kWh, a Levelized Cost of Water (LCOW) of $0.995/m3, and a Levelized Cost of Hydrogen (LCOH) of $2.8/kg with a 99.93% Renewable Fraction (RF). The system design incorporates a hierarchical dual-storage system where batteries are used for intraday balancing and hydrogen storage is used for seasonal energy management. The system design results in a Net Present Cost (NPC) of $7.65 million, a yearly life cycle emission of 287.8 tCO2-eq., and the creation of 297 jobs. Such a system design clearly proves that such a system of integrated renewable energy can serve as a viable model in enhancing water and energy security in arid regions.