Common industrial practices lead to the development of similar software products. These products are usually managed in an ad-hoc way which gradually results in a low product quality. To overcome this problem, it is essential to migrate these products into a Software Product Line (SPL). Towards this direction, this paper proposes a language-independent approach capable of reverse-engineering an SPL from the source code of product variants. A prototype tool and a case study show the feasibility and the practicality of the proposed approach.