More than two years after the bodies of Teresa, Martin and Rudi van Breda were found in their home near Cape Town, South Africa, the man facing trial for their murders has pleaded not guilty in court.

That man is 21-year-old Henri van Breda, the son of Teresa and Martin, and the younger brother of Rudi.

Henri's younger sister, Marli van Breda, just 17 at the time of the attack, was also severely injured. She was discovered on the edge of death; her throat had been slashed and she had suffered serious head wounds.

She managed to survive, but because of her injuries, is not able to remember anything about the night her sibling and parents were killed.

Henri, then aged 20, presented with just a few minor injuries, and raised the alarm with police. He told them an "axe-wielding" stranger had broken into his wealthy family's home, killed his loved ones and knocked him out.

After 18 months of investigations, Henri suddenly surrendered himself to police. He was charged with three counts of murder, one of attempted murder and another of obstructing justice.

But in Cape Town's High Court on Monday, Henri, who once attended Scotch College in Perth, pleaded not guilty, and has denied any involvement in his family's murder.

In a statement read by his defense lawyer, Pieter Botha, Henri said he watched on helplessly "through a crack in the bathroom door" as a masked man wielding an axe attacked and murdered his family.

The court heard that older brother Rudi was attacked first, and his cries for help awoke his 54-year-old father Martin, who "lunged at the attacker".

Henri said his father was "cut down" by the intruder, who he said "was laughing" throughout the attack.

The intruder then attacked his mother and younger sister, before Henri was confronted. His statement described a "life-and-death" struggle, in which he managed to free the axe from the masked stranger before he was stabbed in the shoulder.

Van Breda said he chased the man out of the house before he collapsed and lost consciousness.

His sister Marli is listed as a witness for the state, but the prosecution is yet to decide whether they will call upon her to testify against her brother.

If acquitted, Henri stands to inherit part of his parents' AU$21 million fortune.