So, this may be a bit Alternate-Universe-y, just because I doubt this would happen at Hogwarts, but bear with me...
Severus Snape has taken in an orphan child named Avery (or Sinclair, haven't chosen yet). The child is extremely interested and talented when it comes to Potion brewing, so Snape decides to take him to Hogwarts to become his personal assistant and apprentice. He has the boy sleep in the quarters next to his, and gives him private lessons, causing them to become very close.
Avery takes some classes with other students, but because of the special arrangment, is always focused on Potions. He is sometimes bullied for being different and for hanging around Hogwart's most hated teacher. Avery tries to tell them that Severus Snape is actually a decent, and even gentle man, but few listen.
Eventually it dawns on Snape that he loves his young apprentice, and Avery finds himself finding love and safety in the Professor that gave him a home.
Physically, Avery is a small, slender boy for his age with large green eyes, a small upturned nose, and a few freckles on his pale face. His hair is dark brown and cut all one length at the height of his chin, a bit girlish, and pushed behind his ears; similar to a mini version of Snape's hair. (So cute :3)
Interested? Message me! :)