The tale of Avatar Roku and Fire Lord Sozin is revealed to Aang and Zuko by different sources. Both learn about themselves and are shown the origins of the war.
I’m watching Avatar: The Last Airbender 3×06 “Chapter Six: The Avatar and the Fire Lord” [embedpress]https://trakt.tv/shows/avatar-the-last-airbender/seasons/3/episodes/6[/embedpress]