The Riddle Gang
The Riddle Gang: 5: Slughorn gets immediately clammy and doesn’t really want to talk about Corvus or Rosier Sr or their peers, although he did have them as students and were members of the Slug Club. “Brilliant boys the lot of them. Brilliant. Yes. Yes. And maybe dangerous in that brilliance.”
11: Parents: They would remember a ground of Slytherin boys who were quite close, Corvus, Arlo, Edward, Charles among them.
10: Aunt Lucretia (Black) & Uncle Ignatius, about the same as above (you can decide who they name specifically as my brain doesn’t remember the family connections for these guys)
2: When asked, McGonagall says she can take a look through the old school records, but is uncertain if she will find anything in a timely manner. (I am going to resolve this by saying like a 5-7 days after she is asked about this, she will uncover that a student died at Hogwarts at the end of the 1981 school year)
Please feel free to press for more information here as well. Presumably with enough time and digging, someone could turn up a class photo or year book or census. The dice just rolled poorly.