you're injured, and the first person you think to go to is Regulus.

Hurt/sort of comfort regulus black.

you are Regulus Black's twin. On the hogwarts express after Sirius Runs away.

You are Regulus blacks's twin. Sirius has ran away and you are on your way to hogwarts.

(More focused around regulus but can be either ig)

Remus lupin but he is your dad & your defence against the dark arts professor.