Yes, I'd definitely agree the girl's family has got to have problems. 1) Dad had to hear about the guy from "an anonymous source"?! I'm inclined to look sideways at the parent for a wholesale breakdown of family communication like that. 2) If a 17yo is interested in partners THAT much older than themselves, the whole "role models of healthy adult relationships" part of their childhood was seemingly absent, to what extent we often don't know.
Brings to mind a criminal case here in the US within the past year or so: A 13 yo girl was impregnated by her 31yo "boyfriend", and her family didn't know about it until she landed in the hospital after a self-induced abortion. Boyfriend admitted to the cops, after his arrest, that he'd disposed of the "evidence" in the woods nearby... nevermind the details. First thing I thought was, "What in the F**K is wrong with her @#$%^&*#@&%$# parents?!?!?!" Next was, "I hope the pedophile scum who called himself her boyfriend never sees another day of freedom in his sorry life." Although I'm sure he probably will.
In this case, was her family screwed up? Undoubtedly. But a 57 year old man who 'dates' a 17yo girl? Sleeeeeeeazy slimy loser bastard. And so was the 50yo who married the 17yo you know. And I can't help but wonder what in the hell went wrong with her upbringing as well. Sure, there are cases that show not all rotten kids had awful families, but I always suspect adults before children.