The benefit of using cluster diagrams as the foundation of these multiple coacervation models is that it is possible to systematically combine different theories that are complementary. To illustrate how this can be done, we point out that there are three types of contributions that can be combined without any overlap in meaning, to develop a complex coacervate model. This includes (1) the random phase approximation result for the excess free energy, which includes all ring diagrams, (2) the transfer matrix theory, which accounts for thirdorder multi-site interactions only between pairs of molecules, and (3) the hard core liquid contributions at the beyond-second order level, which are otherwise included in (1) and (2).