Intellectual disability (ID) is a neurodevelopmental disorder with a prevalence of %1-3. Genetic factors contribute strongly to the etiology of ID and it remains unknown in up to 60% of the cases. De novo mutations represents a common genetic cause in sporadic cases of ID. In this paper, we aimed to present two 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 the chromosome 15. These cases are thought to be associated with distal trisomy 10q and monosomy 15q syndromes, respectively. Both trisomy 10q and monosomy 15q are rare diseases with a distinctive clinical profile described.