I feel terrible for this little boy. It's obvious that his parents are ashamed of him because of his medical issue, which is in NO WAY the child's fault. At least half, if not more of all seizure disorders are GENETIC in origin. Evidently no one has told this couple or their families this, however. There is an epilepsy gene, just like there is a gene which causes cystic fibrosis. It sounds like this child may have inherited that gene from one or both parents. They feel guilty because he has seizures, and they are communicating their guilt to him, which is shameful. I'm sure they probably blame themselves, too, and they may secretly be blaming their son for the family's social isolation.
As for the rest of the family, they are just IGNORANT about seizure disorders and what causes them, and this shows. As a teacher yourself, you can probably appreciate the meaning of the old saying about ignorance breeding fear. In this family's case, that really rings true. There's not much you can do except try to be there as a support person for your student as much as possible.