The family of John Edwards' former mistress, Rielle Hunter, is challenging the former senator to take a DNA paternity test after his claim that he did not father Hunter's 6-months-old child.
In the first reaction from Hunter's family, her younger sister Melissa told ABC News that Edwards should immediately follow through on his pledge to take a paternity test.
"I would challenge him to do so," the sister said.
"Somebody must stand up and defend my sister," she said. "I wish that those involved would refrain from bad-mouthing my sister."
Late Saturday evening, The Washington Post reported that Hunter released a statement through her attorney, Robert Gordon, that she would not participate in a genetic test.
Calls to Gordon were not immediately returned.
"I would welcome participating in a paternity test," Edwards said. "I'm only one side of the test, but I'm happy to participate in one."
Hunter left her Santa Barbara, Calif., home earlier this week in advance of Edwards' ABC News interview.
She had been hired in 2006 to produce Web documentaries for the Edwards campaign, at a cost of $114,000, even though she had no filmmaking experience.
Edwards said the affair began only after she was hired. The two had initially met at a New York city hotel bar, according to friends of Hunter.
Her daughter, Frances Quinn, was born in February in Santa Barbara.
Edwards admitted to ABC News he met secretly with Hunter last month at the Beverly Hilton in Beverly Hills, Calif., for the purpose of "trying to keep this from becoming public." As he left the meeting, at 2:30 in the morning, he was confronted by reporters from the National Enquirer.
Edwards told ABC News he had not told his wife about the meeting in advance.
He said the meeting was not "the only contact" he had with Hunter since 2006 when he said he ended the affair.
"There have been some other telephone contacts," Edwards told ABC.
Hunter's sister Melissa said Rielle was being falsely portrayed as a "promiscuous person" and was not involved in "setting up" Edwards at the hotel meeting.
"She is a good and honest person, the sweetest and most caring woman one could ever hope to meet," the sister said.
"Do you think it's easy for us to just sit back and let everyone rip her to shreds and not defend her honor?"