Zuko seems awfully old for Katara, some say Aang is 112, but actually he is 12 and was frozen in an iceberg for 100 years so technically he's ten. I don't think Katara will ever be with Zuko anyway, I mean they're enemies and she really likes Aang, she kissed him for crying out loud and people still say she will go to Zuko! I mean SERIOUSLY!
I can't understand it either.
It's nice with the whole water-fire opposites thing... but آپ can have that with a Sokka/Ty Lee یا Sokka/Azula pairing.