I have this headcannon where even though Sirius always acts like he hates his brother Regulus, he misses being able to talk to his brother the way they did before Hogwarts, and when he finds out about Regulus's death, he locks himself in his room and cries for the little boy he still loved.
Yes yes yes Sirius acted detached but he was he was devastated af when he lost his little brother, baby Reg, and not even James could console him.











