As a result of the speed of information and communications technology convergence, the concept of the business ecosystem has been adopted for understanding the business value chain. Within the business ecosystem, keystones play a central role. Currently, Google and Apple are the keystones of the mobile ecosystem, and they have been quite active in acquiring firms over the past years. This study empirically examines the effects of these two firms' mergers and acquisitions (M&As), especially the different effects on the acquirer and the rival depending on the type of target firm. After the target firms are classified according to the businesses of the acquiring firm that each target firm is related to, the study examines the effects of different types of M&As on the values of the acquirer, the rival, or both. The results provide a basis for understanding the complex relationship between two keystones within the mobile business ecosystem.