JOHANNESBURG -- A 23-year-old South African man was sentenced to life in prison on Thursday for the 2015 axe murders of his parents and brother in an affluent housing estate.

Henri van Breda appeared impassive as a judge sentenced him to three life sentences for the grisly killings of parents Martin and Teresa and brother Rudi in Stellenbosch, a scenic town in a wine-growing area near Cape Town.

Van Breda also received a 15-year sentence in the Western Cape High Court for the attempted murder of his sister Marli at the time of the attacks. She suffered severe head injuries in a bloody onslaught that Judge Siraj Desai described as "cold-blooded" murder.

"These attacks display a high level of innate cruelty," Desai said. "The violence was excessive and gratuitous. It was intended to cause maximum harm."

Defence lawyer Pieter Botha, who plans to appeal the conviction and sentencing, had suggested van Breda's youth and status as a first-time offender should be mitigating factors in the sentencing. He also said his client could not show remorse because he maintains he is innocent.

While Desai recalled that a witness heard a loud argument in the van Breda home for several hours on the night of the killings, he told Henri van Breda that "we have no explanation for what you did" and that he had to be handed the "severest possible penalty."

Van Breda also received a one-year sentence for obstructing justice after the court concluded that he inflicted injuries on himself to try to mislead police.

South Africa's government welcomed the sentencing, saying it "serves as a deterrent to others who think that violence in the family will be allowed in South Africa."

The van Breda family lived in Australia for some years before returning to South Africa, and the judge said Henri van Breda had enrolled at the University of Melbourne.

"Your future was not bleak. In fact, it was bright," Desai told van Breda as he stood in the dock. "You had the support of family and, more importantly, they had the means to assist you in your future endeavours, and it seems to me they would have done so."