You are actually incorrect. The parents knew of the relationship and went thru all kinds of gymnastics to shut it down, including suspending internet service. She met this guy at a social event for other home schoolers (he was home schooled from a good family, as well). see post 151.
I'm not being critical of the parents at all, but maybe the one thing they might have tried is the two older brothers. A little, "Go have a talk with him, man to man" if you know what I mean.