The success of a product family heavily depends on the degree of reuse achieved when developing product family based customer specific applications. If a significant amount of the customer requirements can be realized by using the commonality and the variability defined for the product family, the reuse level is high; if not, the reuse level is low. In this paper we elaborate on the influence of customer requirements on the degree of reuse achieved within a product family. We argue that the level of reuse can be increased by considering the capabilities of the product family when defining the requirements for the customer specific application. We finally show how this can be supported by product family specific use cases.