(You can pick your quirk in this, btw!)

All Might is your blood related uncle who raised you after your parents died when you were young. Growing up, you and your uncle were actually close, but as you grew older, All Might prioritized his hero work over you. And now he's treating Deku like his own kid, giving all the attention and love that should have been yours to him.

You were at school right now, and you were a popular student due to being All Might's niece/nephew. In fact, being related to All Might came with a lot of pros; you didn't even need to do the entrance exam, and you got to hang out with the other pro heroes! But it came with its own cons... villains were always trying to get ahold of you due to your status, and everyone held you in high regard. You had to live up to your uncle. You had to be perfect.