Complex coacervate core micelles (C3Ms), formed through electrostatic interactions between oppositely charged block copolyelectrolytes, are effective delivery vehicles for hydrophilic biomacromolecules. This study investigates the impact of polymer architecture on the C3Ms structure by blending homopolyelectrolytes and diblock copolyelectrolytes as anionic counterparts for cationic diblock copolyelectrolytes. Our results show that the micellar structure, including core size, aggregation number, and corona characteristics, is precisely controlled by the fraction of homopolyelectrolytes. C3Ms formed by the AB + C system have larger core dimensions and aggregation numbers but lower corona brush densities compared to AB + AC systems. These findings highlight that the spatial constraints of polyelectrolytes play a crucial role in determining micellar structure, which can be further understood by balancing the free energies contributed by core block stretching and interfacial tension.