The behavior of a closed system undergoing irreversible aggregation and containing two distinct monomer types is considered. For large cluster sizes and at large times, the size-composition distribution is described by a two-parameter scaling law, which is valid for homogeneous non-gelling kernels. This scaling law is composed of the product of a normal distribution in particle composition and the one-parameter scaling function for the corresponding homogeneous aggregation problem. It is shown that this scaling law also applies to a kernel that depends linearly (and not simply as the total particle size) upon particle composition.