In complex supply chains, individual downstream buyers would often rather replenish from intermediaries than directly from manufacturers. Direct replenishment from manufacturers can be a less costly alternative when carried out by the buyers collaboratively. This paper constructs a general model to study collaborative replenishment in multi-product supply chains in the presence of intermediaries. We introduce a class of associated cooperative games, outline a sufficient condition for their stability, and formulate a lower bound for individual allocations in the core. Drawing upon a class of associated two-stage games, we investigate the choice of allocation rule and its effect on the individuals' strategic decisions about participation in the collaborative organization. We prove that the Shapley value coordinates the supply chain as it makes complete participation the best individual choice for all buyers under complete or incomplete information. We show if the collaborative organization disregards the replenishment options from the intermediaries, so that they would be handled individually, no allocation rule could always coordinate the supply chain.