Iroh

Iroh (also known as The Dragon of the West, and most commonly referred to as "Uncle" ) is a fictional character in Nickelodeon's animated television series Avatar: The Last Airbender. The character, created by Michael Dante DiMartino and Bryan Konietzko, was voiced by Mako in the first and second seasons, but after Mako's death of esophageal cancer, Iroh was voiced by Greg Baldwin in the third season. The short story "The Tale of Iroh", in episode 15 of Season Two, "The Tales of Ba Sing Se", was dedicated "In Honor of Mako".

Iroh is a Firebending master and a former Crown Prince of the Fire Nation, a race of people who can create and manipulate fire. He is a retired General of the Fire Nation, and older brother of Fire Lord Ozai. Iroh accompanied his exiled nephew, Zuko, on his quest to capture Aang, the long-lost Avatar, in order to restore the young prince's honor and rights to the throne.

In "Tales of Ba Sing Se", Iroh’s name was written as 艾洛 (aì lùo).

In the movie his name is pronounced EE-roh

In the second season, Iroh was revealed to be the firstborn son of Fire Lord Azulon and Fire Lady Ilah. Iroh was destined to succeed Azulon as Fire Lord of the Fire Nation. Although the change was never officially announced by Fire Lord Azulon, Ozai became Fire Lord. Even when Ozai had seized the throne, there was never any action taken by Iroh to take back the throne. In The Firebending Masters, Zuko tells Aang that Iroh killed off the last of the dragons, earning him the nickname "Dragon of the West". In reality, Iroh lied to conceal and protect the last two dragons, who had taught him the true art of Firebending. The method that the Fire Nation currently uses gets its source from anger and rage, as opposed to the form that the dragons taught Iroh, Zuko, and Aang, which draws its energy from life. In the 2 hour episode event "Sozin's Comet" it is revealed that he is a Grand-Lotus, or high-ranking member, of an international secret society named the "Order of the White Lotus", which is also composed of Katara's, Aang's, and Sokka's old masters: Waterbending Master Pakku, Swordmaster Piandao, Omashu King Bumi, and Firebending Master Jeong Jeong.

Source: Wikipedia