Hunter, 45, met Edwards, 56, in 2006 at a bar in New York City. A self-described filmmaker, Hunter helped produce four webisodes that chronicled Edwards' course on the campaign trail. The affair between the two was first reported by The National Inquirer in October 2007, an allegation Edwards fiercely denied.
In July 2008, Edwards was reportedly seen visiting Hunter at a California hotel where she was with her newborn child, and a month later Edwards admited to having an affair with Hunter but not to having her baby.
In August 2008, after months of speculation, Edwards told ABC News' Bob Woodruff that he had, in fact, been unfaithful to Elizabeth with Hunter. At the time, he also denied the possibility that Hunters newborn was his own, saying in the interview, "That is absolutely not true."
And Cate, the oldest Edwards child, has also endured the death of her older brother Wade, who was killed when he lost control of the car he was driving near the family's North Carolina home in April 1996.
"This [news of a half-sibling] will be yet another set of issues these kids will have to overcome and deal with," said Reena Sommer, a Texas-based psychologist who specializes in family issues.
"This was a big secret that was kept from them so it's about a breach of trust," she said.
Even so, the Edwards clan will likely still be curious about their half-sibling, who is, after all, a part of the family, said Sommer.
"There will be this sort of catching up and wanting to know once they hear the news," said Sommer. "Sort of like whenever a baby is born and everyone wants to know if it's a boy or a girl, what it looks like and these kids will want to know if she looks like them."
"There will be a ton of questions," she said.