Agglomerations and proximities between firms are positively related to the creation of knowledge networks and the innovation performance of firms. Despite the long history of the study of proximities, only recently have interactions between multiple proximities and multiple networks been studied with respect to the economic performance of clustered firms. The role of personal relations in the creation of business relations between firms needs to be studied further. This study proposes a framework for the creation of business relations that combines the proximity framework, the strategic alliances literature, and multiplexity of social networks. The study uses a novel dataset on the ego-networks of personal relationships between owners or managers and the ego-networks of business relations of biotech firms in Chile. It is shown that the existence of previous personal relations between individuals from two organisations positively affects the probability of creating a business relationship between them.