Avatar: The Last Airbender, Season 3

Zuko:
[confronting Iroh in his cell] You sent this, didn't you?! I found the "Secret History"- which, by the way, should be re-named the "History Most People Already Know!" The note said I needed to know about my great-grandfather's death, but he was still alive in the end!

Iroh:
No. He wasn't.

Zuko:
What are you talking about?

Iroh:
You have more than one great-grandfather, Prince Zuko. Sozin was your father's grandfather. Your mother's grandfather was Avatar Roku.

Zuko:
[in shock] Why are you telling me this?!

Iroh:
Because understanding the struggle between your two great-grandfathers can help you better understand the battle within yourself. [Zuko drops to his knees] Evil and good are always at war inside you, Zuko. It is your nature, your legacy, but there is a bright side. [Zuko glares at him] What happened generations ago can be resolved now by you. Because of your legacy, you alone can cleanse the sins of our family and the Fire Nation. Born in you, along with all the strife, is the power to restore balance to the world.

[Iroh lifts a stone in the floor of his cell and pulls out a cloth-wrapped parcel; he unwraps it to reveal the headpiece that Sozin gave to Roku.]

Iroh:
This is a Royal artifact. It's supposed to be worn by the Crown Prince. [he offers it to Zuko, who takes it]