The aim of the study was to examine the impact of familial learning disabilities (FLD) on the phenotypic profile of 47, XXY males and the possibility that 47, XXY males with more severe cognitive deficits may be partially a consequence of familial dyslexia/reading disorder. We wondered if FLD could pose an additional risk for complex neurodevelopmental differences in 47, XXY. The neurodevelopmental profile of males with 47, XXY has been characterized by developmental dyspraxia, language-based learning disorders, executive dysfunction, reading, and attentional deficits. One hundred eighteen boys with 47, XXY diagnosed prenatally who did not receive early hormonal treatment were divided into two groups based on positive histories of FLD and given comprehensive neurodevelopmental evaluations between 36 and 108 months. The assessments included intelligence (nonverbal and verbal), neuromotor (fine and gross), speech, and language. The group with FLD performed significantly lower in multiple neurodevelopmental domains of the Wechsler of VIQ P = 0.015, FSIQ P = 0.0005, the Brief IQ P = 0.0525 of the Leiter, in Auditory Comprehension P = 0.0505, Expressive Communication P = 0.0055, and neuromotor domains of Manual Coordination P = 0.0032, Fine Motor Control P = 0.0378, and Motor Coordination P = 0.008. Our study demonstrates the influence of FLD on neurodevelopment and expands the phenotypic profile of 47, XXY, suggesting some neurodevelopmental variability is attributable to other factors than the additional X. FLD may increase the vulnerability of the 47, XXY children and anticipatory guidance should be provided to families. © 2014 Wiley Periodicals, Inc.