- Oscar Pistorius is set to be sentenced on Tuesday
- CNN spoke with his brother and sister
- Whatever the sentence, their lives have changed permanently, they said
On the eve of Oscar Pistorius' sentencing, some of his biggest supporters -- his siblings -- told CNN that the lives of everyone close to the trial have already been changed forever, no matter the outcome.
Pistorius, 27, is due to be sentenced Tuesday for culpable homicide and one weapons-related charge in connection with his fatal shooting of his girlfriend, Reeva Steenkamp.
"No one who's been close to the situation can just overcome it," Aimee Pistorius said. "It's something my brother will carry with him forever and ... regardless of what's happening now it's just a certain phase in a journey that will never end."
Aimee Pistorius was in the courtroom throughout the trial, and the first to come over and console her brother during breaks in the proceedings. She has also been quiet about the case, declining to speak to the media until now.
As the defense attorneys have argued, she said there is no reason to doubt that her brother believed an intruder was in the bathroom who posed a risk to him and Steenkamp when he fired shots through the toilet door.
Aimee Pistorius said she was shocked when she first heard about the fatal shooting.
"But also knowing my brother -- his insecurities, who he is -- the very first thing that came to my mind is that it could have only been a mistaken identity for an intruder and that's because I know my brother and I know his fears," she said.
State prosecutor Gerrie Nel has called for a minimum prison sentence of 10 years for the athlete.
"This is a serious matter," Nel said at the end of the arguments over sentencing. "The negligence borders on intent. Ten years is the minimum."
There is no legal minimum sentence for culpable homicide in South African law, so it will be up to the judge's discretion.
The sentencing will bring a close to one chapter of the case, but an appeal is possible.
"It's never going to be over," Aimee Pistorius said. "Something like this changes my brother's life, our lives, the Steenkamps', their family, their friends."
CNN spoke with Aimee and her brother Carl Pistorius at the home of a family member in Midrand, South Africa.
The trial was beset by drama at times, and the most difficult thing for the Pistorius siblings in watching it unfold is the sense of loss.
"That is a heart-wrenching pain, having lost our mother at a young age -- it is an anguish that you feel when you know that someone else is going through deep, deep pain," Carl Pistorius said.
Whatever the court decides, public opinion has been harsh on Oscar Pistorius, which both siblings said had affected them.
There have even been reports of threats by gang leaders in prison against Oscar Pistorius that have the family worried.
"Absolutely, any threat needs to be taken seriously. So we are obviously concerned for his safety," Carl Pistorius said.