I think environment can make a OK jaw quite bad, but not really bad. Really bad comes from really bad genetics (e.g.hapsburg lip) or quite bad + bad environment, IMO. I had a friend in highschool with an open bite and who absolutely crying out for bimax surgery and she had the exact same face as her mother. She got braces but she doesn't look too different today.
In my case I have the exact same facial structure as my father but my jaw recession is significantly worse. Now, is that because I'm female, because of poor growth at some point childhood (indicated by poor enamel in my 1st molars) or a side effect of extractions and orthodontics? Or an example of a trait getting more exaggerated down the generations This often happens when there are lots codon repeats in the gene. It's easier to go from 30 to 31 repeats of a codon than it is to go from 5 to 6, the checking mechanisms miss the extra codon. The older the father, the more it tends to happen and the more the extension. Now, I don't know anything about jaw genetics but it's not too much of a stretch to imagine. My father was 40 when I was born; kids of older father's have more genetic defects.