Regulus watches, hidden, as she pulls out her wand, face impassive - almost impossibly so - calmly removing her eldest son's name from the tapestry. He doesn't understand how she can be so emotionless in the face of this… development, as she calls it.
Sirius had always been the favourite child, right up until the point that he had been sorted into the wrong house, and even then she'd still held out some hope for him. He was the eldest, after all; the heir to the House of Black. He was the child she had always dreamed of, and Regulus simply was not.