Okay. I know we've talked about things, but in case of those I haven't talked about, you can find my ten (omg, why) here.
Micah - Of all of mine, Gage is probably the most interesting to Micah. But Ric and Daisy have a passing interest in Borgin & Burke's stock. Micah and Reg were in the same year.
Alecto - Reg is the most obvious connection as they were Slytherins in the same year. She may know the names of my nobles: Marietta Edgecombe, Katrina MacDougal, and Marguerite Rosier.
Sam - We've talked about Ric, who adopted her as his mascot with his other Ravenclaw friends. So there's that! Um, yeah. He's protective of her, but I don't know if he always admits it. Kitty is a Gryffindor a few years older and would have been friendly. Both Ric and Anthony are in her year. Justin's friendlier than Anthony, but if Sam can deal with Ric then Anthony is a breeze. Kit's a year younger, but he legit wants to be friends with everyone.
Severus - Friendly with Reg? Otherwise, Severus would have had all my other characters as students. Ric (smart and the potential to do better, but wasn't interested. Didn't make it into NEWT). Mari (did everything by the book and wasn't memorable for any real reason. Didn't make it into NEWT). Justin (did his best, wasn't a troublemaker, adequate student. Didn't make it into NEWT). Anthony (dyslexic and was terrible at note-taking and his essays were initially a mess, once he was able to adapt, he was an excellent student. Took NEWTs). Kat (essays were wonderful and well-thought out. she was decent in practicals. Didn't make it into NEWTS). Gage (unmemorable student, but passable. Didn't take NEWTS). Daisy (breakout star of her year, in his house. Took NEWTS. Still sees him as a mentor). Kit (absolute troublemaker, but if tricked/challenged into doing his work did extremely well. Took NEWTs). Percy (know it all, did everything by the book. Took NEWTs).