Iroh and Ozai, it's the same story if you discount the crucial changes in the ending.
The tale had become propaganda over the recent decades, and the books that once held the original had burned along with the rest of the Fire Nation's texts in the Great Library; but oral versions close to truth were still passed down, if the right people were asked.
The story went like this:
At the very start of things, there were only three elements.
This is obvious, if you think about it. We stand on the ground, we breathe the air, and we drink the water--but while we see the sun and know that it causes things to grow or die with its presence and absence, it's much farther away than the rivers and earth and wind. So while there were surely some people who felt more drawn to the sun than to the mountains or the ocean or the high places near the sky, they wouldn't have understood their longing.
Most priests and scholars believe that the first fire was created by a storm. A low bolt of lightning, an old tree--these are our origins, a combination of the strength of water and the productiveness of earth.
Of course, the fire couldn't have lasted long, not in pouring rain! The first time that a fire must have burned long enough to be discovered was either the result of a lightning storm or an active volcano. And even then, our element wouldn't have been of much use until the people learned how to incorporate it into the others: to feed it from wood or grass but set it down on rock, to keep water at a safe distance, and to be wary of the air--a little wind can snuff a fire, but too much will send it raging.
But once fire was understood, those people who had not felt quite at home in the mountains or the plains or the shore also came to understand what they had been longing for. And this is why the Fire Nation has such spirit and pride in itself and its people.
"Because our strength comes from the strengths of the other nations. We are the last element, but also the one that brought balance to the whole," Iroh concluded. He paused a moment, before adding more quietly, "As we are trying to do now," and then chided his son for not finishing his tea.
"Because all elements give us strength," Ozai told his son and daughter as they sat below him, training complete for the day. "The wind, the earth, even the rain--all of them can fuel fire, if controlled and used properly.
"That is all for today," he added, and Azula and Zuko bowed and prepared to leave.
Gods are crumbling somewhere, machines are rumbling somewhere.