There was a man who had a dog for 14 years. He had this dog when he was a teen, and into his adult hood. Eventually he decided that he wanted to pass on his family name. He didn't want to get married however, as he was Asexual. He looked for possible donors that would birth his child, and donated sperm to the person. 9 months, 4 days later his child was born.
It was a baby boy.
This baby boy was an ordinary boy, a bit stronger then most, and a bit more intelligent. The doctors believe that the boy was gifted, and the father was over joyed.
The father raised his child, with his dog. He was a very happy father, and he pulled in more then enough money to live comfortably.
Then, 2 years later. The boy was playing in the kitchen with the dog. And when they were playing he bumped into a standing table and knocked over the contents onto the floor. One of which was a steak knife from the fathers dinner the previous night. The knife fell off that table, twirling in the air... and then found its target. Right on the back of the dogs neck.
When the father came home and saw the dead dog, and the boy smeared in its blood... He snapped.
The fathers first reaction was to beat the kid. In his mind he was thinking that he was being good for his child. He was teaching it right and wrong. And even though the child was screaming, the father knew deep down that this was the proper way to raise a child. But the father knew that the world was not accepting of this way. He knew he had to hide it.
That night. the father moved the sons bed into the basement, and covered the windows with foam and wooden boards. He hung shackles from the ceiling,and moved down text books so the boy could learn.
The father knew that the best way to raise his son would be through violence, and books. He will make his son smart, and pass on his legacy. That is the only reason he was born. To pass on his fathers genes.
Years go by, and the boy became incredibly smart, he was very good at mathematics, and even in the circumstances his English was decent. Although speaking was still a bit of an issue.
Finally after 13 years of this (meaning he's 15) his birth mother decides that she would just like to see how the child is doing. Mostly out of curiosity, but partially due to the fact that she misses the child, despite only being together for such a short time.
She asks the father if she can see the child. The father was acting a bit strange, but allowed her to visit. The father cleaned the house that day, cleaning off the old dog blood stains on the kitchen floor, and did something to mask his sons smell. Oh how his son smelled poorly. He would beat him later to teach him the proper way to clean up your blood.
The mother visited the next day. She was confused why the child couldn't come up stairs and began to worry. She agreed to go downstairs to visit, thinking that maybe an accident happened, or if he was still asleep. It Was 7 am. Perhaps he was sleeping in on the weekend.
The mother went down stairs. And saw her son. She began to cry. Surrounding the son was blood, he had scars all over his naked body. There was a slide show playing in front of him with lessons. The mother rushed towards the boy to try to save him.
The boy turned his head towards the strange women, and felt a connection. Like he knew her, but he did not.
The father shocked the women with a tazer he had in his pocket and murdered her with a knife on a near by table.
The father then started cutting the boy chanting "Todays lesson... DON'T FUCKING CRY".
The boy resolved to escape some how. He decided next weekend when his father lets him off the chains for his intensive exercise that he would make contact with the outside world some how. That Wednesday however, he didn't have to. A police officer knocked on the door asking about a missing women, and was wondering if the father knew anything. The father panicked and shot the police officer in the neck through the door.
A swat team broke into the house 4 hours later, and shot and killed the father. They discovered the son and sent him to a hospital immediately.
The character then goes to a psychiatrist for 1 year, and is released. The boy is apparently insanely intelligent for his age, but does have some communication problems, and has no people skills what so ever. He doesn't trust anyone, and expects every person to only want to taunt and maim him.
The character begins from here. He can go in any direction, of either being a psychopath, to developing people skills thanks to friends, or anything.
Hope this helps.
*edit
Sorry if this doesn't make sense, I've been typing this for the last 5 minutes, and it's about 5:30 am here.
I need to get some sleep @.@