Vampire Knights: The Prefects' Pasts

I feel like all anime writers must be somewhat sick or depressed in order to be successful. The amount of time they put into making their characters absolutely miserable must be immense. It seems like every one in three characters has either been abused by their parents, or been in a near death experience. The past is a mysterious thing in anime, and Vampire Knight focuses a lot about uncovering our protagonists' past. Both Yuuki and Zero share similarities in their childhood experiences, however one comes out with a thankful bond, while the other is bonded by the chains and ropes of pain and sorrow.

Yuuki's Past

Yuuki may be the most mysterious character of this whole series. Though she is our main character, we still know nothing about her past, and she doesn't know either! Her earliest memory is that of Kaname saving her from a blood thirsty vampire. That explains her deep admiration of Kaname and the thanks she says that she owes him. Her fear of vampires is mixed with the gratitude and safety she finds in Kaname, yet tainted with the image of the evil vampire's fangs.  

Zero's Past

Zero and the pureblood vampire, Shizuka Hio, which bit him

Zero's story truly is depressing. He comes from a family of top class vampire hunters, and was the victim of a pureblood's wrath. His father, mother, and his brother were said to have been killed by her. He was the only survivor, and faces the future of being a vampire himself. His whole life seems to revolve around reaping revenge over that one vampire. His transformation into a level E vampire creates a deep hatred of himself. He hates the fact that he struggles everyday with his blood lust, and despises the fact that he has to drink Yukki's blood in order to survive. Yuuki sees his pain day by day, and realizes how hard it must be for him to have to become that of which he despises. 

I have to say, I'm more curious about Yuuki's past than Zero's. I'm wondering why Kaname is only nice to her. Is it because he sees her as a little sister, or is there something more behind that? Also, why doesn't she know anything else about her past? If I had to guess, I'd say that Kaname erased her memory, and that Kaname and her must have had some relationship before Yuuki lost her memory.