This talk will follow the discussions found in https://arxiv.org/abs/1711.04773 and https://arxiv.org/abs/1902.04082. We will discuss the cosmological implications of the Co-Decaying Dark Matter Model--a recently proposed mechanism for depleting the density of dark matter through the decay of nearly degenerate particles. This model generically predicts the existence of an Early Matter Dominated phase of universe evolution. We will show that this phase promotes sub-structure growth and solar mass primordial black holes.