|Robert Pattinson and Kristen Stewart|
A source told The Sun on Sunday newspaper: "They pretty much decided they couldn't live without each other.
"Kristen poured her heart out to Robert and told him it was a one-off and a mistake."
After the revelations Kristen, 22, had cheated on the 26-year-old hunk with married father-of-two Rupert, Robert moved out of their Los Angeles home.
However, he has now accepted Kristen's apology for her "stupid mistake" and the pair want to move on with their relationship.
The source added: "Rob sees it as Kristen made a really stupid mistake. After a lot of long tearful talks, they've worked it out.
"Rob can see how truly sorry Kristen is and has totally forgiven her. They really do love each other."
The pair - who have moved back in together - are due to appear on the red carpet together in November for the final 'Twilight' film 'Breaking Dawn - Part 2'."