Growing up, the ballroom was about the etiquette expected of being a member of the Black family. After becoming a Granger, it was something else.
There was a moment of clarity for Regulus one New Year's Eve, in foolish stubbornness the rest of the family would have associated only with his older brother.
Hermione asks her father how he got his scars.
Sebastian knows that isn't his name, particularly after the faded tattoo marred with scars darkens and starts moving.