We present a mean-field theoretical molecular model capable of addressing the disparity in results drawn from experiments studying the structural and thermodynamic characteristics within multicomponent anionic model membranes. The experiments were drawn under identical system conditions, differing only in lipid preparation method_electrophoresis, in the presence of sugar solutions, versus a gentle hydration protocol, absent of sugars. The discrepancies in the membrane phase behavior were noted, but left uncharacterized due to constraints on the experimental conditions that limited the yields necessary to evaluate a comparison drawn between the techniques.Such experimental limitations highlight the utility of our theory, from which we can capture the non-trivial coupling between organizational and physiochemical properties within the system. We use a molecular model to quantify the isolated and net contributions of glucose, sucrose, and counterion distribution to the stability of phase-coexistence regions in ternary anionic membranes comprised of dipalmitoylphosphatidylcholine (DPPC), anionic dioleoylphosphatidylglycerol (DOPG), and cholesterol. The theory is based on a free energy formulation that explicitly accounts for the architecture and charge distribution of all system molecules, while treating the intermolecular interactions within a mean-field approach. A distinguishing attribute of our theory is the rigorous construction of all system components from a molecular foundation, realistically characterizing the system's physics on the scale of the monomer. The size and shape of each monomeric unit are treated explicitly, and all possible conformations, as well as a comprehensive set of translational and rotational states, are included.As delineated in this work, anionic lipid head-regions present hydroxyl groups capable of forming hydrogen-bond networks. The introduction of sugar molecules motivates strong interactions with these networks, tremendously disrupting the stability of phase coexistence regions. Screening of counterions partially alleviates this effect.