MCGONAGALL: Do you think it wise to trust Hagrid with something as important as this?
DUMBLEDORE: Ah, Professor, I would trust Hagrid with my life.
Hagrid is Dumbledore's family, in deed if not in blood. That helps define what this film thinks of family, and how it means far more than just your blood relatives.
MCGONAGALL: Albus, do you really think it's safe, leaving him with these people? I've been watching them all day. They're the worst sort of Muggles imaginable. They really are...
DUMBLEDORE: The only family he has.
Here, Dumbledore is strongly emphasizing the ties of blood. Even though Harry's a black sheep (and worse) to the Dursleys, they're not about to turn him away, which is what Dumbledore needs.
HAGRID: Didn't think your mum and dad would leave you with nothing, now didja?
Glad to know the Potters were keen financial planners. Money solves some problems.
HARRY: But I've never even played Quidditch. What if I make a fool of myself?
HERMIONE: You won't make a fool of yourself. It's in your blood.
RON: Whoa! Harry, you never told me your father was a Seeker too.
HARRY: I didn't know.
Just as Harry finds out about who he is during his first year at Hogwarts, he also finds out who is his parents are—and in the case of Quidditch, where his identity and his parents' intersect.
HARRY: Excuse me! C-could you tell me how to—
MRS. WEASLEY: How to get on the platform? Yes, not to worry, dear. It's Ron's first time to Hogwarts as well. Now, all you've got to do is walk straight at the wall between platforms 9 and 10. Best do it at a bit of a run if you're nervous.
This is a bit of foreshadowing, indicating how much of a family the Weasleys will become to Harry. But it also gives a glimpse of Ron's family, and more importantly, shows what a kind woman his mother is.
RON: Happy Christmas, Harry.
HARRY: Happy Christmas, Ron. What are you wearing?
RON: Oh, Mum made it for me. Looks like you've got one too!
HARRY: I've got presents?
Harry's genuinely shocked that he actually has Christmas presents…which infers both that the Dursleys were an awful family to him, and that he's finding a newer, better family at Hogwarts.
RON: Harry, do you think this mirror shows the future?
HARRY: How can it? Both my parents are dead.
A bracing dose of reality in the face of some powerful magic. As much as Harry loves his mom and dad, they're gone…and he's wise enough to recognize it.
VOLDEMORT: Haha. Bravery. Your parents had it too. Tell me, Harry, would you like to see your mother and father again? Together, we can bring them back
The devil always tempts you with what you want the most. In this case, he's offering Harry a family again.
DUMBLEDORE: Harry, do you know why Professor Quirrell couldn't bear to have you touch him? It was because of your Mother. She sacrificed herself for you. And that kind of act leaves a mark. No, this kind of mark cannot be seen. It lives in your very skin.
HARRY: What is it?
DUMBLEDORE: Love, Harry. Love.
Mom loves you, Harry. Don't ever forget it.
DUMBLEDORE: And finally, it takes a great deal of bravery to stand up to your enemies, but a great deal more to stand up to your friends. I award 10 points to Neville Longbottom.
Just so we're clear, Neville's part of this family too. And like all family members, he fights with his brothers and sister sometimes…though always for the right reasons.