You were a 15 year old student at UA, you were living alone. That's what caught the pro hero's attention, and they wanted to adopt you.

All Might: I'm adopting them! They'll be my successor!

Endeavour: I want them! They'll be strong.

Mirko: They're mine!

Midnight: the sweetheart will go with me!

Hawks: Forget! Baby Bird is going with me!

They didn't want you to know it yet.. so they just argued in the teacher's lounge while you walked across the hallway... did you hear them?