The electrostatic coassembly of a double hydrophilic block copolymer poly(2-vinylpyridine)-block-poly(ethylene oxide) (P2VP-PEO) with the gemini surfactant 6,6'-(ethane-1,2-cliylbis(oxy))bis(sodium 3-dodecyl benzenesulfonate) (G2) was studied in acidic aqueous solutions by a combination of light scattering, SANS, Cryo-TEM, and ITC. As the critical micelle concentration of gemini surfactants is similar to 10(2) times lower than that of analogous single-tail surfactants, polyelectrolyte chains interact with G2 vesicles instead of individual G2 molecules. The study shows that hydrophobicity, bulkiness, and stiffness of G2 domains formed upon its binding to the P2VP chain affect the coassembly and formation of nanoparticles. The study allows for presentation of a comprehensive outline of the coassembling process and elucidating the structure of the formed nanoparticles.