This is a soulmate AU, but it is not romantic. It is platonic, except for Suki and Sokka. Everything else is familial, and I won't be changing that. Ok? Ok. Also, this is based off a lovely fanfiction on Archive of our own, under the name "The family you choose". It's great, and I honestly believe you should go read it before this.
Zuko pov
I had always hoped to know who my soulmates are, but the marks had been removed, by my father, the second he saw them when I was born. The only thing I even know about them, from my mother, is what color they might be, but she caught only a glimpse and was on sedatives, so she's unfortunately not a good source to get my information.
Azula and father had no marks, they just didn't deserve them, or didn't get them, but they don't have marks. I know what elements my partners use - one airbender, one waterbender, one earthbender, and 2 non users - and that really limited down my options, especially once I realized the avatar was the only Airbender and is soulmates with Katara, Sokka, Toph and Suki, to figure it out. Honestly, I'm just glad they've not yet realized I'm the sixth.
They don't know Fire nation symbols well, and so my mark, whatever it is, won't be recognized for years to come - by which point I will already be dead - because to keep yourself from your soulmate, is to accept death. You don't have to stay with them 24/7, but after meeting them you have to hang out for a few hours at least, but I know mine won't know until too late. A week after not going to your soulmate, the pain becomes too much and you die.
The pain will come from the marks and will spread color along your body until you're covered, but every inch of skin the color takes, even if the lines look smooth, are filled with gut - wrenching, want to end it all pain. I would know, after all, I'm currently lying on my bed, not too long after noon, with a pillow in my mouth to mute any sounds I make, and my shirt off.
Even with the marks no longer seeable, they are still causing pain, simply because I know who they are. It's not worth it, I'm not worth it, and the pain is something I'll take, because I have taught him and the others enough they can make it on their own. Even if they can't, I left letters, maps and other information I thought would be useful, for them to use once I passed. They won't like me, not with what little they know about me.
I was a complete asshole to them, and the little they know about me, will absolutely not be enough for them to want to them. I know I deserve this, and so much more, but this is the only way I can think to make even slight amends. I did not do anything for the other 5, and I'm assuming they never even felt my spirit during their youth.
I bury a scream in the pillow as agony lights up my torso. I moan and squirm, trying to fight, even when I know this is what I deserve. I wince as sunlight streams in my eyes, but fight back the agony enough to get up. I have to show up for breakfast and a last training lesson with Aang, before heading back to my room. Hopefully the fact that the marks are growing will not be noticed.
I groan, but stand shakily and drag on my shirt, even as the feel on my shirt agitates the pain and makes it worse. It won't be for long, and then I can return to my room, look at the photo of Uncle Iroh and die in peace. The other 5 don't need to know I was their soulmate, it won't bother them, not with how little, if at all, my spirit probably interacted with them when they were younger.
It takes a few more minutes for me to get steady enough to walk, and pull up my shield, so that they don't suspect a thing. It won't do if they suddenly realize I'm their soulmate and decide to actually save me. I wince with the first few steps, but by the time I'm in the main room with the others, they can't see anything wrong. I see a frown on Toph's face, but nothing seems off so I shrug off the frown and settle down next to her.
I take the bowl from the Katara with a small thank you, aware she's not my biggest fan, if she even likes me. I don't think any of them like me, not even Toph, who, while civil, is certainly completely on my side. I don't want to hurt any of them more, so I continue to pretend that everything is ok, even as the agony spreads to my feet, and continues to grow, causing an un noticeable - unless you're looking for it, and none of them are - shake in my hands.
I finish and offer Katara my bowl, aware she won't take my offer to help, after a full week of trying, even though I have been acting as good as I can. As I lead Aang to his last firebending lesson - though he doesn't know that, and is happily talking about the lesson after this - while the agony moves towards me shoulders. I wince, hiding my face from Aang, as we move into the last stance. I let him move through the entire thing, fixing his mistakes and offering small praise when he does good.
"Alright, that's it. We're done!"
"Awww... Do I have to?"
We both know he has to, but it's an inside joke we have going. I should do my usual response, give him a 'no, but I like living and being a breathing person' joke, but honestly, I can't make it myself right now.
"Yes, you must. You know Katara would skin me if you're late. I'm going to my room, not hungry and I need a nap, I didn't sleep well."
I know this will not only keep him from checking in with me later, but it will also stop anyone from coming into my room until a later time, by which point I will already be dead. It won't matter at that point and nothing else can keep me from dying. Aang pouts but nods and I grin, before heading off to my room, acting normal up until I'm past his view and then collapsing against the wall.
I work my way through the Air Temple, knowing the others are all where they should be and even if I collapse, only Toph might notice, with all the things she picks up. I'm only hoping she can't pick me up right now, since my heart is fluctuating between rapid, and slow.
"Come on...You can do it... Get back to your room... And die in peace... Without letting them know."
I continue to mumble under my breath to encourage myself to move further, finally reaching my room. It took far too long, and I barely manage to open the door and close it behind me, before I sprawl onto my bed. I grunt at the impact and try to decide if I want to remove my shirt, before deciding it's just too much effort. I curl up and bury my face in the pillow, letting the agony show now. I feel my heart slowing down, each beat hurting, every breath ragged, and even the simple act of curing up hurts, agony coursing through every vein in my body.
I scream into the pillow, and then everything starts to fade, the world, the colors, the light, everything. I feel surreal, almost like I can feel everything, but it's just so distant and it's fading, what is this pain, I just want it to go away. The colors are the last thing I can see, and then everything becomes dark.
..........Still Zuko pov, hours later ..........
When I wake, the agony is gone and I have faint memories - tears streaming down Aang's face, Suki and Sokka's horrified, Katara's angry, Toph's defensive, but they all look slightly sad, even Katara - before the after affects hit me and I moan, but I can tell this is less than the pain during the week long suffering.
"Zuko!?!"
I moan, but open my eyes. Everything's blurry, but as it comes into focus I can't help but notice how red both Aang's and Toph's eyes are, while Katara is nowhere to be found, and Suki and Sokka are both in the corner, watching me. I wince as I shift, and finally realize I'm shirtless, something I was not when I was dying.
"...Hi?"
They both burst into tears, and even though it hurts, I panic - sitting up - to try and calm them both down. They bounce the second I'm up, wrapping arms around me that could break a bone, but are soft, gentle almost, in their touch. I return the hug, even if awkwardly, and try to sooth them. The four arms are then joined by four others and I lean into them, even if I really just wanted to let them be free.
"How.Could.You?"
"W..What?"
"You were just going to let yourself die and not ever tell us we were your soulmates? The only reason we even found out was because Toph felt your heart and told Sokka, who decided to check on you. We found the colors, and we knew immediately who you were, only Airbenders have that color and even though the marks are burned off - not cool by the way, dude - we decided we needed to help you. You were the only soulmate we could all agree on when we decided to give one more affection then the others."
I blink, but sigh. Of course they'd discover my plan and ruin it. They always managed to escape or ruin my plans, even when they really shouldn't have been able to. It's just there thing. I squeeze the teens in my arms, and grin, deciding this might not be too bad.
"...How mad is Katara?"
"Depends. How long have you know we were your soulmates?"
"It's really only been since we got here. I never saw the marks, burned off at birth, and so until the colors started spreading, the only thing I had was that there was more than one. I found out after the colors started spreading, and that's when I decided to stop being a burden. I figured with the stuff I've done to you, it's only fair I leave with less trouble. I left you maps, information, everything I thought you'd need, even told you to make Uncle Fire Lord. So why did you decide to help me?"
There's a nice silence, and everyone pulls back, though only to get closer. Sokka and Suki slip behind me, settling beside each other against the wall, while Toph and Aang stay in my lap. Surprisingly, it's a female voice from the doorway that answers me.
"We decided to help you, because you are the best soulmate ever. I don't know how you were raised, or why, but the reactions you have once we each bond is not something any of us will ever forget. You're soul, being a firebender, is warmer, and because of that we could always tell your emotions. You would get hotter when you were angry, colder when sad, and a nice warmth - though we all ultimately decided you use different heats for each of us - when you decided we needed comfort. It was another of the things we ultimately agreed on : you were easily able to help each of us with our own problems, in unique ways. None of us change our ways, but you mold for every one of us and we decided that in turn we would help you out as best we could."
I blink and then turn to find Katara joining us on the bed, settling in nice and comfy. I let everything she said settle in, and decide not to say anything for fear it will ruin the moment.
Here's the link to the story, for those who couldn't find it.
https://archiveofourown.org/works/20383669/chapters/48345097