Why does Ponyboy love Darry in The Outsiders?

The complex relationship between Ponyboy and Darry is
initially explored in the first chapter of this classic work of fiction, when Ponyboy
tells us how he feels that he loves Sodapops more than anyone else, including his
brother Darry. Note what he tells us about his relation with his elder
brother:

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[Soda's] always happy-go-lucky and grinning,
while Darry's hard and firm and rarely grins at all. But then, Darry's gone through a
lot in his twenty years, grown up too
fast.

We are in addition told
that Darry works "too long and hard" as he has been left, as the eldest brother, to look
after Sodapops and especially Ponyboy. However, it is clear that in spite of the way
that Ponyboy appreciates and understands something of the sacrifices that Darry has had
to make to look after them, he also is annoyed by the way that Darry is always
"hollering" at him and treats him as if he were "six instead of fourteen." It is only in
the final chapter, after Sodapops forces the brothers to become reconciled to each
other, that Ponyboy realises that he does love Darry and that Darry loves
him:

I
suddenly realised that Darry was only twenty, that he wasn't so much older that he
couldn't feel scared or hurt and as lost as the rest of us. I saw that I had expected
Darry to do all the understanding without even trying to understand him. And he
had given up a lot for Soda and
me.

Thus we can see that
Ponyboy loves Darry for the way that he has sacrificed so much to keep the family
together, in spite of the way that he so often tells off Ponyboy and shouts at
him.