There was a family in the small town that I used to live in where the mom and dad were first cousins. They had 3 kids, 2 boys and a girl. The girl is really slow, and can barely talk (shes 18 years old) then the 2 boys seem to be ok. The oldest graduated a couple years ago, and the youngest boy is going into gr.12 next year. So whether the girl is slow because of her parents could be, or it could just be a coincidence.