Software product line approach has been successfully adopted in various software domains. In some fields, single SPLs are no longer sufficient to fulfill their requirements due to the large variability amount they include. Consequently, a set of separated SPLs is built to handle this issue and construct what is known by Multi Product Lines (MPL). However, the emergence of MPLs results in several challenges, namely: managing the reuse between SPLs, structuring the MPL model and distributed derivation. In this paper, we propose a new approach for SPLs composition. Our approach relies on two main concepts: the separation of concerns and the partial derivation. It is validated in the context of an e-Learning MPL and an illustration is explained throughout the paper. The results show that our approach helps systemizing reuse within MPLs and structuring the MPL model. Moreover, SPLs are integrated early in the development process avoiding thus the distributed derivation challenges.