Genetic algorithms with sharing are well known for tackling multimodal function optimization problems. In this paper, a sharing scheme using a clustering methodology is introduced and compared with the classical sharing scheme. It is shown from the simulation on test functions and on a practical problem that the proposed scheme proceeds faster than the classical scheme with a performance remaining as good as the classical one. In addition, the proposed scheme reveals unknown multimodal function structure when a priori knowledge about the function is poor. Finally, introduction of a mating restriction inside the proposed scheme is investigated and shown to increase the optimization quality without requiring additional computation efforts.