Narcissa had never held any love or affection for Sirius Black, but she did grieve when he died. She didn't grieve for the man. No, she grieved because Sirius's death marked the death of the Black name.
Narcissa had been a Black, but she had lost that name when she had married Lucius. She had never cared about that, however, because she loved Lucius. And she was still proud to be a Malfoy, even if it was just by marriage and not by blood.
But Narcissa was also proud to be a Black, and it grieved her greatly to see that name die along with Sirius.
Neither Sirius nor his younger brother Regulus, who Narcissa had loved, had left any heirs behind to continue the family name. Only Narcissa and Andromeda had produced heirs, but those heirs did not carry the Black name. Instead, the heirs carried the names of their fathers.
The Black family had once been so grand and so huge. It had once been one of the largest Pureblood families. But now it was as if the Black name had never existed. It was forever dead.