"An unhappy alternative is before you, Elizabeth. From this day you must be a stranger to one of your parents. Your mother will never see you again if you do not marry Mr. Collins, and I will never see you again if you do." (18.20)
To be honest, knowing that we'd never see Mrs. Bennet again is definitely motivation enough not to marry Mr. Collins. (As though we needed any more.) But we should point out that "see" here means more like, "recognize" or "acknowledge." Basically, Lizzy is being threatened with being disowned—a very real possibility. Well, probably not for refusing to marry someone. But, in most families, Lydia could well have been kicked out forever.
Her father, contented with laughing at them, would never exert himself to restrain the wild giddiness of his youngest daughters; and her mother, with manners so far from right herself, was entirely insensible of the evil. […] Catherine, weak-spirited, irritable, and completely under Lydia's guidance, had been always affronted by their advice; and Lydia, self-willed and careless, would scarcely give them a hearing. They were ignorant, idle, and vain. (37.17)
Yikes. The worse we've ever said about our little siblings is that they were being pests, and even then we didn't really mean it. How is it possible that the five sisters are so different? And would having good parents really have made a difference?
But she had never felt so strongly as now the disadvantages which must attend the children of so unsuitable marriage, nor ever been so fully aware of the evils arising from so ill-judged a direction of talents; talents, which, rightly used, might at least have preserved the respectability of his daughters, even if incapable of enlarging the mind of his wife. (42.3)
You know that painful moment when you realize that your parents aren't perfect? Lizzy probably never had to experience that with her mom, but this is the moment she figures out that her father isn't quite as awesome as she thought. Unpleasant, sure—but it's a crucial part of growing up.
"Do not make yourself uneasy, my love. Wherever you and Jane are known you must be respected and valued; and you will not appear to less advantage for having a couple of—or I may say, three—very silly sisters." (43.20)
Just one more example of how little Mr. Bennet understand about the way family works. It's like a nightmare version of the Three Musketeers, you know, one for all and all for one: what Lydia does reflects badly on the entire family. (But we have to ask: if Kitty and Mary had been sensible, would Lydia's personality have mattered less? Could four good reputations outweigh one bad?)
"Lydia will never be easy until she has exposed herself in some public place or other, and we can never expect her to do it with so little expense or inconvenience to her family as under the present circumstances." (43.15)
And that, Mr. Bennet, is where you're wrong. He thinks that sending Lydia to Brighton to get her kicks out will minimize the damage, but it actually ends up almost destroying the family. Good thing Darcy steps in to save the day—and to keep the family respectable enough to marry into.
"If you, my dear father, will not take the trouble of checking her exuberant spirits, and of teaching her that her present pursuits are not to be the business of her life, she will soon be beyond the reach of amendment. Her character will be fixed, and she will, at sixteen, be the most determined flirt that ever made herself or her family ridiculous; […] Oh! my dear father, can you suppose it possible that they will not be censured and despised wherever they are known, and that their sisters will not be often involved in the disgrace?" (43.18)
Mr. Bennet thinks that Lydia's behavior isn't going to reflect badly on Lizzy or Jane, but he's wrong. Maybe if he ever left his library to supervise his daughters at one of those balls where they make themselves ridiculous, he'd actually know something about how the world works.
Their visit did not continue long after the question and answer above mentioned; and while Mr. Darcy was attending them to their carriage Miss Bingley was venting her feelings in criticisms on Elizabeth's person, behaviour, and dress. But Georgiana would not join her. Her brother's recommendation was enough to ensure her favour; his judgement could not err. (45.12)
Now, this is how to do family: Georgiana agrees with her brother's every opinion. If only our brother felt the same way. (To be fair, Darcy is actually right about this one.)
"Not so hasty, if you please. I have by no means done. To all the objections I have already urged, I have still another to add. I am no stranger to the particulars of your youngest sister's infamous elopement. I know it all; that the young man's marrying her was a patched-up business, at the expence of your father and uncles. And is such a girl to be my nephew's sister? Is her husband, is the son of his late father's steward, to be his brother? Heaven and earth! —of what are you thinking? Are the shades of Pemberley to be thus polluted?" (56.63)
We forgive you for getting a little confused with all these uncles and nephews. We're not saying family doesn't matter, but Lady Catherine really seems to be taking it a step too far. It's like she thinks she's going to be polluted by being very, very, very distantly related to Wickham.
Kitty, to her very material advantage, spent the chief of her time with her two elder sisters. In society so superior to what she had generally known, her improvement was great. She was not of so ungovernable a temper as Lydia; and, removed from the influence of Lydia's example, she became, by proper attention and management, less irritable, less ignorant, and less insipid. From the further disadvantage of Lydia's society she was of course carefully kept, and though Mrs. Wickham frequently invited her to come and stay with her, with the promise of balls and young men, her father would never consent to her going. (61.4)
Family can drag you down, so here's a nice example of it actually lifting someone up. By spending time with the right sisters (Jane and Lizzy), Kitty becomes a little more tolerable. (But notice that she doesn't actually gain any positive character trains—just becomes "less" annoying.)