My son was diagnosed with alpha-thalassemia x-linked intellectual disability syndrome. The questions I have relate to other members of the family. I have a sister who has children. I understand that if my sister has the mutation, there is a chance that she passed it to her daughter, who would then be a carrier. But the literature I have read isn't completely clear regarding boys. If my sister carries the mutation, could she have passed it to her son and could her son be an unaffected carrier of the mutation?