Yet he didn't kill his father until Ursa came up with a plan to do it so she could save Zuko, didn't kill Iroh, smiled in disdain when Zuko said he would help the Avatar defeat him, and constantly endangered Zuko and Azula despite having no other heirs. Furthermore, the show clearly wanted to push Azula and Zuko's rivalry - adding another sibling would force their attention (and ours) to shift to said sibling, which is why Kiyi only was created in the comics that were focusing on the royal family, after Zuko became Fire Lord, and even then she is Ursa's daughter but not Ozai's, meaning Azula is still the only real 'rival' Zuko has. If they went to such lengths to avoid creating too many characters, it makes sense that Zuko and Azula have no step-mother and no half-siblings in the show. Avatar is a very mature kid's show, but it is still a kid's show, with characters who control the elements and don't get a single scratch on them in situations that would severely injure or kill a normal human being, and the writers likely didn't want to add more characters to an already complicated, political plot like the Fire Nation Royal Family - which is why Iroh never remarried, Azulon's wife was already dead, there were no Lu Ten flashbacks, etc. until we remember that the only noble family in Avatar that has more than two kids is Ty Lee's, and that there are people like Kyoshi who literally over two centuries old when she died. It would be very strange for Ozai to never try to have more heirs, and constantly endanger the ones he does have. So Iroh defeat = Ozai trying to usurp the throne = Azulon's piece of shit death to Zuko demand = Azulon gets murdered, sorry assassinated = Ozai usurping the throne anyway (although I'm not sure Iroh really fought him on that at all? Someone please clarify) = Ozai being firelord when Zuko spoke up = the whole agni kai business = Zuko having his face burnt by his own father and told he's weak and is given a frankly impossible task = Iroh watching on and feeling shame, disgust, guilt, and honestly I ultimately think he felt fear for Zuko and fear of having to acknowledge more than ever before that his younger brother and even the nation he loves are on the wrong path and that power isn't worth the amount of pain and suffering caused, like I'm sure previous to this he knew, he had to have known because we know how incredibly intelligent Iroh is, and we also know he is part of white lotus (which again someone might have to tell me a timeline on that because the white lotus thing seems to have being going on a while so was he white lotus during the ba sing se seige? The first one I mean? OH THOUGHTS BUT I'LL COME BACK = Iroh and Zuko's pirate adventures uh, I mean Zuko tries to capture the avatar and Iroh drinks tea = Iroh having to watch Zuko struggle at an impossible task to regain honour he never actually lost = Iroh being a scheming old man to achieve the goal of giving Zuko a loving father = Iroh going on the journey with Zuko to befriend the gaang = Iroh participating with other white lotus members to liberate ba sing se = leading to help the downfall of an oppressive regime = Zuko taking the throne in a state of empathy and acceptance.

He's also one of the only people around Zuko that acknowledges he is literally a 13 year old child (when exiled, 16 during the show) the gaang also make acknowledgement of this but considering they themselves are like 12-15 approximately this acknowledgement doesn't have the same impact as GROWN ASS ADULTS thinking it's okay for the firelord (a powerful force) to fight agni kai against a 13 year old and then exile him for having.an opinion? Like honestly do these people actually know what the agni kai was about and just accept that or are they told Zuko did something terrible.which like even so pretty poor form here y'all (anyway I digress clearly from my point but I have FEELINGS and probably there are other people with in the fire nation that have enough empathy and critical thinking to know that what happened to Zuko was wrong but my point remains) Uncle Iroh is one of if not the only ADULT character that seems to actually be shown as thinking Zuko is a child with feelings instead of that he's dishonoured his family or that he's evil. Iroh has first hand knowledge what being on the wrong side gets you.

Firelords raiment