Ursan

Ursan is the second born prince to the Fire Nation and a firebender. He is a firebending prodigy, who became a master at the age of 13, and even mastered its sub-skill of lightning. He also knows how to redirect lightning, as it is a family tradition to learn it. He became Terra's overall firebending teacher and went on the road with her.

Before Terra
Ursan was born to Fire Prince Zuko II and Princess Nana on 196 AG. He was the second born prince, with his brother, Vikram, preceding him, and his sister, Aki, succeeding him. Growing up, he was a firebending prodigy. He understood it greatly, was able to execute it just as greatly, and didn't let the power go to his head either. He was perfectly happy with Vikram taking the throne because it left him with so many options in life. He may have not have had the power Vikram would have, but he would have freedom to do as he pleases.

One month before Terra comes, Zuko asks how Ursan would feel if he were the one who inherited the throne after him and not Vikram. Ursan politely declined, saying that Vikram would be a much better match for the throne, and Zuko agreed.

Personality
He's energetic and easily excitable. He can also be hot-headed. Ursan embraces the idea of freedom from being a royal. He wants to explore the world and understand different cultures and people. He also wants to have as much fun as possible in as many places as possibles. Weirdly enough, he's a lot like Aang as a kid in that aspect.

He's also impatient, as noted when he tried to tutor Aki in her firebending and got so frustrated when she didn't understand what he said automatically that he blew a hole in the wall. Vikram took on her tutoring sessions from then on. When he was trying to explain to Terra what her mind block was in firebending, he almost burned a tree to a crisp in frustration.

Ursan is also very competitive, as he starts a lot of races and spars with Anil and Terra.