The `Twilight Saga` actor - who was left devastated after discovering his girlfriend of four years had cheated on him with her `Snow White and the Huntsman` director Rupert Sanders - has decided to give the actress another chance after realising he can`t live without her.
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`."