== Birth == 
 This seems to be missing a key piece of information. 
 "Their birth was normal, and they were able to lift their heads and make eye contact with their parents within hours after birth. Doctors at the time referred to this behavior as related to a seizure disorder and speculated that both girls would become mentally retarded as a result." 

 What behavior was termed a "seizure disorder"? The sentence that precedes it doesn't indicate anything abnormal.