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 six-month 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." In his interview with ABC News correspondent Bob Woodruff...