But at age 12, his life took an unexpected turn. He came down with a strange illness. The doctors weren't sure what it was, but their best guess was cryptococcal meningitis.
He got progressively worse. Eventually he lost his ability to move by himself, his ability to make eye contact, and then, finally, his ability to speak.
His parents, Rodney and Joan Pistorius, were told that he was as good as not there, a vegetable. The hospital told them to take him home and keep him comfortable until he died.
But he didn't die. "Martin just kept going, just kept going," his mother says.
His father would get up at 5 o'clock in the morning, get him dressed, load him in the car, take him to the special care center where he'd leave him.
"Eight hours later, I'd pick him up, bathe him, feed him, put him in bed, set my alarm for two hours so that I'd wake up to turn him so that he didn't get bedsores," Rodney says.
That was their lives, for 12 years.
Joan vividly remembers looking at Martin one day and saying: " 'I hope you die.' I know that's a horrible thing to say," she says now. "I just wanted some sort of relief."
And she didn't think her son was there to hear it.
But he was.
"Yes, I was there, not from the very beginning, but about two years into my vegetative state, I began to wake up," says Martin, now age 39 and living in Harlow, England.
He thinks he began to wake up when he was 14 or 15 years old. "I was aware of everything, just like any normal person," Martin says.
But although he could see and understand everything, he couldn't move his body.
"Everyone was so used to me not being there that they didn't notice when I began to be present again," he says. "The stark reality hit me that I was going to spend the rest of my life like that — totally alone."
Martin and his father, Rodney, in the 1990s.
He was trapped, with only his thoughts for company. And they weren't particularly nice thoughts.
"No one will ever show me tenderness. No one will ever love me."
And of course there was no way to escape. He thought, "You are doomed."
So he figured his only option was to leave his thoughts behind.
That was his first strategy — disengaging his thoughts — and he says he got really good at it.
"You don't really think about anything," Martin says. "You simply exist. It's a very dark place to find yourself because, in a sense, you are allowing yourself to vanish."
But occasionally there were things that elicited thoughts he could not ignore.
Like Barney.
"I cannot even express to you how much I hated Barney," Martin says.
Since all the world thought Martin was a vegetable, at the special care center where he spent his days he was often in front of the TV watching reruns of the children's cartoon hour after hour, day after day.
Then one day, he decided he'd had enough. He wanted to gain some small measure of control over his day. So he figured out how to tell time by how the sun moved across a room. That was the start.