It is shown that many features of the recombination luminescence attributed to bound multiexciton complexes (BMEC) in Si can be understood in terms of a shell model. Zeeman and stress-split spectra of phosphorus BMEC's are explained by the model and luminescence lines which were originally predicted by the model have been observed. A qualitative interpretation of the energies of the BMEC recombination photons is given. The intensities of acceptor bound exciton and BMEC luminescence lines are explained for the first time. A formal treatment of no-phonon recombination in indirect gap semiconductors is given and related to the observed spectra.