It was a disturbing story, told in a Pennsylvania courtroom: a girl and her five sisters, living in virtual sex slavery for years, starting when one of the girls was just 7. The defendants were their parents, who had fallen under the influence of a child rapist who cast himself as a prophet and took care of their finances after they left the Amish faith.

“Just incomprehensible,” the Pennsylvania judge said Wednesday as he sentenced the parents to the maximum allowed by law.

The authorities said the man, Lee D. Kaplan, 52, was a cultlike figure who brainwashed the family and created a world in which “child rape was the norm.” He fathered two children with the oldest girl, the first when she was 14.

Mr. Kaplan was convicted last month on 17 counts of rape of a child, statutory sexual assault and other offenses. He faces sentencing in September.