Intellectual disability (ID) is defined as a neurodevelopmental disorder. The prevalence is 1% to 3%. Genetic factors strongly contribute to the etiology of ID; however, the origin remains unknown in up to 60% of the cases. De novo mutations are a common genetic cause in sporadic cases of ID. This report describes the cases of 2 siblings with distinctive phenotypical features and neurodevelopmental disorders with an unbalanced translocation, (46,XX,der[15]t[10;15][q24.3;26.1]mat), resulting in trisomy of the long arm of chromosome 10 and monosomy of the long arm of chromosome 15. The cases are thought to be associated with distal trisomy 10q syndrome and monosomy 15q syndrome. Both trisomy 10q and monosomy 15q syndromes are rare diseases with distinctive clinical profiles.