Autism is believed to be a disease that is triggered when genetically susceptible children are exposed to an unknown toxin. This was originally thought to be the mercury in thimerisol vaccine preservatives, but autism rates have continued to rise, even though thimerisol and mercury have been largely phased out as vaccine preservatives. Now evidence has appeared that autism might have a stronger genetic component than previously believed.
This is because the mothers of two children in New York, both of whom have autistic children, turn out to have had the same sperm donor. While sperm banks will not reveal the identity of donors, there is a website called Donor Sibling Registry which can arrange meetings between offspring of the same donors.