This is Ganymede, or as he prefers to go by, Nim. He is a powerful Seer and is also a seventh year Slytherin. He tends to give off a vibe of not really caring much about anything. He is prone to sarcasm though can also be quite charismatic.
He is also blind, having lost his physical sight when his Seer powers began growing exponentially during his pre-hogwarts childhood. He is aided by a working class seventh year Slytherin boy that his parents are funding in exchange for his assistance. Nim also always carries an enchanted staff that helps him find his way around places.
Some cliff notes:
He is a Slytherin who is in his final year.
He takes Arithmancy, Astronomy, Charms, Defense Against the Dark Arts, Divination, Transfiguration classes.
The bulk of his friend circle would likely be made up of other boys. Class and blood do not wholly matter though he would likely have been in the same kiddie circles as other UCPB kiddos.
He has a part-kneazle cat that operates much like a seeing eye dog and is also very protective of Nim.
He would possibly have a younger friend in Violetta in his house, Arithmancy and Charms are among her better subjects so they might have shared interests there, she also dislikes herbology (i see that P) as she thinks it's a bit grubby. Regarding his blindness he might enjoy the feel of the expensive French fabrics that Violetta often has delivered as little gifts from her parents that she likes to show off.
As a tenous link Dorothea Potts is the governess of another blind student so they may have interacted as she would be quick to react to signs that he also needed help and would attend things with Hyacinth that possibly nim might see.
Hello!! My best option is definitely Sirius Black, who is a year above him - Sirius finds the Sight to be a bit off-putting but Nim being UCPB would keep him from being like... actively antagonistic. But passive antagonistic, sure!