Carl and Aimee Pistorius were able to visit the double-amputee track star for nearly two hours yesterday morning at Pretoria's central prison, the Sunday Times reported.
Pistorius is technically allowed five hour-long visits per month, the paper said.
His siblings also brought balloons, gifts and a birthday cake bought outside the prison, which would usually not be allowed, the paper said, while their vehicles did not appear to have been searched.
Because of his physical disability, Pistorius, sentenced in October, is being held in the prison's hospital ward.
The fallen Paralympian gold medallist shot and killed his girlfriend Reeva Steenkamp at his upmarket home in Pretoria in the early hours of Valentine's Day in 2013.
He said he shot the 29-year-old model four times through a locked bathroom door because he thought she was an intruder. He was found guilty of culpable homicide, escaping a harsher murder conviction.
The application for appeal is set for December 9.
