Let me tell you, being the eldest of the as of yet to be born Todoroki brood was a trip. It took me an embarrasingly long time to even realize that was one of those Todoroki. It wasn't until my quirk showed up that I even caught onto who I really was. To be fair, I had no point of reference besides the name Todoroki. It's not like Hien had existed until I was born. Endeavor wasn't around and besides mother's white hair, I had no other clues about my identity. As far as I was aware, the only Todoroki children were Touya, Fuyumi, Natsuo, and Shouto, in that order. Yet here I was. And here I thought it was Dabi who was supposed to be Endeavor's secret love child.
I'd known I wouldn't have Endeavor's perfect quirk long before I developed it. My hair wasn't split colored like the future Shouto would have. Instead, it looked more like an inverse of what Fuyumi's hair would look like, red hair with white streaks. None of the other Todoroki's had my specific coloring, so I couldn't know for sure what my quirk would be, but I had some guesses based on what I knew about their quirks. I assumed I would end up with a fire quirk like Touya eventually would since Natsuo and Fuyumi ended up with ice quirks, so I was quite suprised when I finally did get my quirk. It wasn't flashy like my siblings' quirks, in fact, I was certain Endeavor considered me his biggest letdown with a weak quirk. My quirk was Heat Transfer, which is pretty self explanitory, I could take heat from one source and transfer it to something else. I couldn't directly create heat or cold, but superheat anything and it's liable to combust, just like how anything cold will start freezing over on its own. Most people wouldn't hear temperature quirk and think, "that'd be perfect for hero work!" but the same could have been said for that Tintin-looking Bethesda glitch third-year from the series. In the words of one of that character's friends, he made it into a strong quirk. I could do that too.
I wasn't really one for heroics, and I'm sure in any other circumstance, I'd try to avoid the plot and stay safe, but I ended up here, the eldest child of the number two hero and older sibling of one of the future main characters and possibly antagonist if the whole Dabi thing wasn't resolved. That theory hadn't actually been confirmed when I'd still been alive, but seeing my cute baby brother's face, who'd been conceived almost immediately after I got my quirk, it was obviously true- or at least, it would have been. I had no intention of letting him go down that road if I could help it. By the time Fuyumi, Natsuo, and then Shouto were born, each of us being 3-4 years apart, I was pretty much raising Touya myself. Endeavor didn't care for any of us and while mother tried her best, her favoritism shone through with our younger siblings sometimes and I wasn't putting Touya through that.
As the oldest, I was already well into my teens by the time Shouto was born, a first year at U.A. in fact. Part of my bonding process with Touya was geeking out over heroes. I had instilled a deep admiration of heroes like All Might- especially All Might; I think at this point Touya would manage to go toe to toe with Midoriya in the fanboy department- and even tried to nudge him on the path to heroism. Hell, even vigilantism would've been acceptable to me. Luckily, it didn't go that far. With me as a buffer, and with my quirk able to mitigate the harmful effects of Touya's quirk on his body, his hatred of our father didn't go into criminal territory.
As the baby, Shouto was to be protected at all costs. Especially against our parents. When I was busy with hero studies, I enlisted Touya- and later Fuyumi and Natsuo- to look after Shouto. We had four years to make sure our baby brother knew he had a loving support system that would burn the world for him. Mother even looked less haggard seeing us all care for each other. I started up a tradition of sleepovers in an attempt to circumvent the boiling water incident, which was somewhat successful. Shouto got away unscathed thankfully, but I let my temper get the best of me and slapped her. After that, we agreed it was best if she went away to visit her parents for a while. Endeavor never found out since I swore my siblings to secrecy. Just because I was upset with her, didn't mean I didn't understand why she did it. She might need help, but she didn't deserved to be locked up.
By this time, I was a year out of school and into my career as a sidekick. With mother gone often, I ended up taking over my siblings' care. Touya was just beginning at U.A. himself, so I arranged for him to have his own aparment with the excuse that it was closer to school. Natsuo often spent time over there that I was sure he would move in as soon as he was allowed. Fuyumi and I remained at the estate, mostly for Shouto's sake since Endeavor would never allow us to take him. He missed our brothers, but understood that they didn't want to be around that man any more than he did.
Things were...stable for the next ten years. I wasn't the strongest hero- even Touya outranked me quickly after he went pro- but over the years, I'd made connections, consolidating power, even got a teaching job at U.A., anything I could to prepare for shit to hit the fan. I might not be able to stop what was coming, but at least I could help my brothers weather the storm.