ABSTRACT INTRODUCTION 14 years old female monozygotic Malay twins presented to Pekan Orthodontic Specialist Clinic, Pahang with the chief complaint of proclination of upper teeth. After detailed examination, a diagnosis of Class II division 1 incisor relationship on a skeletal 2 base with average vertical proportion was established for Twin A and Twin B. Both had convex profile, incompetent lips, increased overbite, and increased overjet which was 7 mm for Twin A and 6 mm for Twin B. Twin A’s malocclusion was further complicated with an unerupted supernumerary tooth between the upper central incisors. METHODS Twin A had been referred to the Pediatric Dental Department in Hospital Tengku Ampuan Afzan (HTAA) for surgical removal of the supernumerary tooth. The treatment plan for both twins was: Upper and lower fixed appliances with extractions of upper first permanent premolars, lower left second permanent premolar, and lower right first permanent premolar. Both had anchorage reinforcement through a transpalatal arch. Levelling and alignment as well as orthodontic space closure was carried out for both twins. Despite both twins having presented with a similar malocclusion and skeletal base, as well as similar treatment mechanics, Twin B had a residual overjet at the end of the space closure phase. Taking into consideration of patient’s expectancy towards treatment, Twin B was then treated with a Class II corrector, known as the Forsus fatigue resistance device (FRD) Appliance to continually address the unresolved overjet of 6 mm. The FRD was an alternative to orthognathic surgery to correct the residual overjet with minimizing the risk. Both twins underwent five years of orthodontic treatment with a total cost of RM 1400. RESULTS The post-treatment results were satisfactory for both Twin A and Twin B with both having an overjet within normal limits at the end of treatment. CONCLUSION The treatment outcome of monozygotic twins can be different as tooth movement is greatly influenced by the individual biological response. The functional fixed appliance was effective in resolving the residual overjet in Twin B thus negating the need for surgical intervention and the associated five-fold increase in cost.