We calculate the field-theoretic functions of the generalized dynamical model C(*') , where two conserved secondary densities are coupled to a nonconserved complex order parameter (OP), in two-loop order. A transformation to "orthogonalized" densities can be performed where only one secondary density with nontrivial static coupling to the OP exists while the second one remains Gaussian. The secondary densities remain dynamically coupled by the nondiagonal diffusion coefficent. General relations for the field-theoretic functions allow us to relate the asymptotic critical properties of model C(*') to the simpler model C(*) with only one conserved density coupled to the OP. The nonasymptotic properties, however, differ as can be seen from the flow of the dynamic parameters, which is presented for the case of a real OP with componets n=1,2,3 .