“...but that doesn’t make them all autistic.”
Well, the articles I’ve seen say they were all diagnosed as autistic. This family has 6 autistic kids: https://abcnews.go.com/GMA/OnCall/story?id=4245377&page=1
Six?! Autism must be genetic, at least in some cases.
With all the issues autism brings, multiplied by four, maybe the grandfather couldn’t take it anymore.