avocado_love has written a bunch of stuff, both Avatar and otherwise (HP). That's her fic LJ, so you can find a list of all her stuff in the top post.
Another Brother is my favorite of her work. Would you believe a story about Zuko joining the Water Tribe could actually be believable? It totally and 100% works here. And as an added bonus, Zuko as a little kid is the cutest thing ever. (I had mentioned to gmth in a comment that I remember almost none of the HP fics I had read, but there is one story I do recall: Harry and Snape becoming little kids together (somehow Dumbledore did it from the afterlife). Another Brother reminds me a lot of that: Zuko is given a second chance to have his life come out differently. He's still 100% IC, but because his environment is different, things develop in a different way.)
Ah ha! I found one of the two lost ones. foxysquidalso (another fic-only LJ) writes some really good stuff, too. If asked, I would have said I don't like AUs, but apparently I do since I keep falling in love with them and recommending them! Opposite of avocado_love, foxysquidalso writes the characters as much older (40s in most of the fics I read, but series-aged in some of the others). In her fics, Jet never saw Uncle firebend his tea warm, so the Jet/Lee (or Li) stuff goes differently. :D
The Lee/Li thing kills me. So many people spell Zuko's alias as "Li" when it's pronounced "Lee". I read Li as Lie, not Lee. :/