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Objective: The aim of this study was to compare typically developing siblings of children, who were diagnosed with autism spectrum disorders, with typically developing children matched by sociodemographic characteristics, in terms of finger length ratio and hair whorl features and evaluate the concept of the broad autism phenotype. Methods: Forty-one typically developing siblings of 41 cases who were diagnosed autistic disorder, Asperger disorder and pervasive developmental disorder-not otherwise specified according to DSM-IV-TR and 43 controls of typically developing children, who has no history of any psychiatric disorder in their family, were included. Psychiatric diagnostic interview were applied to all children who admitted to the study. The length of the second and fourth fingers of both hands were measured in the study and control group. Hair whorl features of males, who admitted to the study, were assessed in both groups. Conclusion: 2D/4D ratio of both hands were significantly lower in study group. The hair whorls of males in study group were significantly more counterclockwise rotated when compared with control group. Discussion: In our study it is assumed that the findings according to finger ratio were consistent with extreme male brain theory, which is identified for autism before. A significant difference of the direction of rotation of hair whorl in males, which is a biological finding of lateralization, indicated that there may be disruptions in the normal development of lateralization in typically developing siblings of autism. [Anadolu Psikiyatri Derg 2016; 17(6.000): 506-514]