If you think your family is embarrassing, try having a satirical father, an idiot mother, two hopeless flirts for youngest sisters, and a nerd for a middle sister (and not the cool kind of nerd). Yeah. Lizzy's motto is basically "mo' sisters, mo' problems." And in the world of Pride and Prejudice, your family's behavior reflects on you. If your sister runs off with the high school dropout who owes money to some really unsavory characters, it reflects badly on you. But if she dates the all-star quarterback, you're in for some reflected glory—and you might even end up dating on the b-string.
Austen doesn't care how much Mr. and Mrs. Bennet love their kids; they're still bad parents.
In the novel, young people are influenced by their friends much more than by their parents.