And I do agree with you on the mixed thing. I always imagined Blaise's father being Italian or of Italian descent -- hence the Italian last name. Or Zabini could be Blaise's mother's last name and she herself is racially mixed. So many possibilities here.

Or Blaise could be like one of the characters in the book I am currently reading, whose many-times-married mother gave him the name of the man she was married to at the time of his birth, regardless of biology. :o) Or he could be like my mother, who is African-American on both sides, but her family's surname is Chinese. In fact, her pet side project is tracing her lineage to find out where the name came from.