Case presentation: The case reflect 10-year-old twins who consulted for their anterior overlap. The comparison between the twins is done through clinical and cephalometric investigation. The clinical examination revealed a great resemblance between the two patients both at the extra-oral (ortho-frontal profil, nasolabial angle, the shape of the forehead, cervico-chin distance) and intra-oral view (Palato- position of the maxillary lateral incisors, molar class I, mandibular arch perfectly identical with mirror effect), Cephalometric analysis revealed a very high morphological similarity (identical skeletal class III, biproalveolia, hyperdivergenc and the position of mandibular incisor).

Conclusion: The existence of a very important genetic control on craniofacial development and the installation of dysmorphosis is undeniable, in particular on skeletal class III and hyperdivergence. But the severity of these dysmorphosis can also be increased by environmental and behavioral factors.