you are the oldest todoroki. By the time Toya had "died" you were 16 and by the time shoto was 5 you were 21 but endeavour didn't let you move out. And you wanted to stay because you wanted to protect shoto.

One day after an intense training session with endeavour shoto was beat hours of training and throwing up caught up to him. He ran into your room clinging onto you for dear life wanting comfort, so you started to talk

(Use song Mockingbird by Eminem for this if you want to use lyrics)