I don't own Avatar the Last Airbender.
The Prince is born in early winter. The midnight moon is full and spreads cool light.
His father proclaims him weak. Says that there is no spark in his eyes. He will not have a non-bender for his first born child. His mother pleads with her husband to let her keep her child. The Fire Sages agree. And so the Prince's father relents.
When dawn comes and the sun rises, the Prince screams his life to the world.
The Princess is born in late winter. The midday sun shines bright and lays down rays of warm light.
She is born weak and sick, with eyes closed as if asleep. The healers try but there is nothing they can do. They tell her parents that she will die. The Princess's father pleaded with the Spirits to save her and under the full moon brings her to the Spirit Oasis. He places her in the pond and as her hair turns white she begins to cry.
The Princess's father had two visions that night. One of is a beautiful brave girl becoming the moon. The other vision is faint and flickering, it is of that same girl standing beside a Fire Nation Prince, both of them smiling.
In sleep the Prince and the Princess dream. They dream of each other and play together.
It is years before anyone realizes the dreams are more than just dreams.
I doubt I will update this story very often as it is a lesser priority then Zuko of the Pokémon or Heir of Roku. But I do plan for the story to be wildly canon-divergent. Canon events will not survive Zuko's childhood.