I don't own any of these characters. This is not connected in any way to my other Avatar fic, Thoughts of the Princess. I wrote this in an attempt to explain why Ozai is the way he is.

Explanations

Ozai and Iroh got along tolerably well as children, despite, or perhaps because of the vast differences in their personalities. As they grew older, more independent, more aware, Ozai's respect for his older brother diminished. He did not think Iroh had the cunning and ambition an heir to the Fire Nation throne ought to have. Nevertheless, for the sake of the family and because their father adored Iroh, Ozai was polite to Iroh.

Much to Ozai's annoyance, Iroh proved himself a great warrior and leader. The younger son, in an effort to distance himself from his elder brother, to establish his own identity, became everything Iroh was not: cunning, cruel, devious and ambitious. Ozai proved himself in battle as well, even there differing from his brother. Ozai's troops obeyed him because they feared him. Iroh's troops obeyed Iroh because they respected and trusted him.

Around the time Ozai came of age, Iroh married. Iroh's wife was beautiful and intelligent. Iroh loved her very much, and she him. Soon she bore him a son, whom they named Lu Ten. All was well for several years. Then tragedy struck. Two weeks before Lu Ten turned four, Iroh's wife caught a particularly virulent flu while visiting her family. Three days later, she was dead.

So terrible was Iroh's grief that the royal family feared he would take his own life. Iroh eventually pulled himself together for the sake of his son. The doctors whispered that without Lu Ten, Iroh would not have lived to see the end of the year. They were punished for voicing these thoughts in the royal family's hearing, though Ozai privately agreed with them.

Ozai met a beautiful young woman named Ursa. She was a lady of good standing in the court of the Fire Lord, and Ozai fell in love with her. They eventually married. Though he loved her, he always kept a sliver of distance between them, remembering Iroh's experience with love. She gave him a son, and two years after that, a daughter. Ozai was delighted. Those were the good and happy years. Ozai's happiness and ambition for himself and his family grew. Yet, in the back of his mind he always remembered his brother's sorrow, remembered that to love made you weak. Gradually, he pulled farther and farther away from Ursa.

The final stroke that killed Ozai's love for Ursa fell when Lu Ten died. Iroh was completely broken, paralyzed by grief. He failed in his mission to take Ba Sing Se. He withdrew to mourn and grieve, and this time they were certain he would not recover. Iroh stopped eating, and the doctors feared that one day he would quietly fade away.

The fresh tragedy impressed itself in Ozai's mind, the very proof he needed that love was too dangerous to hold.

Azulon commanded that Zuko be killed for Ozai's ambition. To Ozai's dismay, Ursa proved to be as stupid about love as his misguided brother. She offered to kill Azulon herself, so that Zuko might live. He agreed, but told her she must leave and never return after the act.

On that day, Ozai's heart turned to stone.