The swimmer's father has prostate cancer, and mother has breast cancer.
Johannesburg: South African Olympic swimming champion Chad le Clos, who beat Michael Phelps in one of the upsets of the 2012 London Games, announced on Monday that both his parents are fighting cancer.
Le Clos said in a statement that his father Bert, who himself became a global celebrity for his exuberant celebrations and animated interviews in London, has prostate cancer and underwent surgery last month.
His mother Geraldine has breast cancer, had a double mastectomy, and is undergoing chemotherapy, Le Clos said. Le Clos' mother had been in remission since 2010, but the cancer had returned, Le Clos said.
"It has not been an easy time but I am training hard for Rio," Le Clos said in his brief statement . "More than anything else I want them to win their battles. I also hope that they will be in Rio."
Le Clos asked for privacy for his family and said he would not be doing any interviews ahead of the Rio de Janeiro Olympics, which open on Aug. 5.
Le Clos, just 20 at the time, beat his childhood hero Phelps to win gold in the 200-meter butterfly in London, a big surprise that gained added attention because of his father's heartwarming and humorous TV interviews.
Admiring his son with a gold medal around his neck, Bert said in an interview with the BBC soon after the race: "Look at him! And he's beautiful! Look at this. What a beautiful boy!"
The father then asked if the interview was going out live. When told that it was, Bert apologized for being so excited.
Fans loved Bert so much that the BBC asked him to return for a second interview.
Chad le Clos, now 24, is due to defend his 200 butterfly title in Rio, and also compete in the 100-meter butterfly, where he won silver in London just behind Phelps. He could come up against Phelps again in those two events. He could also swim in the 200 freestyle.
Le Clos is also a three-time world champion and a six-time winner at the world short-course championships.