Harry Potter and the Sorcerer's Stone
How we cite our quotes:
I really don't think they should let the other sort in, do you? They're just not the same, they've never been brought up to know our ways. Some of them have never even heard of Hogwarts until they get the letter, I imagine. I think they should keep it in the old wizarding families. What's your surname, anyway? (5.184)
Here, Malfoy sets up a connection between family and class. The "old wizarding families" are, to him, a higher class than the "other sort," who haven't been brought up to learn magic. Ironically, even though Harry can be thought of as practically wizarding royalty, he's in the same ignorant position as many mixed-blood wizards, and he is himself only one-generation pureblood.
Everyone expects me to do as well as the others, but if I do, it's no big deal, because they did it first. You never get anything new, either, with five brothers. I've got Bill's old robes, Charlie's old wand, and Percy's old rat. (6.150)
Having "five brothers" is a problem to Ron, because of the pressure of doing well and putting up with all the hand-me-downs, but it must seem somewhat exciting to Harry. Ron's complaining about having too much family, and Harry's never had enough.
The Sorting is a very important ceremony because, while you are here, your house will be something like your family within Hogwarts. You will have classes with the rest of your house, sleep in your house dormitory, and spend free time in your house common room. (7.7)
This statement is truer than McGonagall knows. For Harry, especially, his "house" is "like [his] family within Hogwarts"; it's also just like his family. He's practically adopted as an honorary Weasley, and he's far happier at Hogwarts than he ever was at the Dursleys'.