Robert Pattinson was preparing to propose to girlfriend Kristen Stewart ahead of cheating scandal, reports say

Robert Pattinson and Kristin Stewart are stars of one of the biggest vampire franchises of all time, the "Twilight" saga. (AP)

“Twilight” star Robert Pattinson was gearing up to propose to his longtime girlfriend Kristen Stewart when the news of her affair with her married “Snow White and the Huntsman” director broke, according to several published reports.

Last week, Stewart, 22, confessed to a “momentary indiscretion” with Rupert Sanders, 41. After Us magazine obtained a photo of the two in a steamy embrace, Stewart issued a public apology to Pattinson.

“I am deeply sorry for the hurt and embarrassment I’ve caused to those close to me and everyone this has affected,” Stewart, who has been dating her “Twilight” co-star Rob Pattinson for several years, said in a statement. "This momentary indiscretion has jeopardized the most important thing in my life, the person I love and respect the most, Rob. I love him, I love him, I’m so sorry.”

Sanders, who has two children with wife Liberty Ross, also chimed in with a public apology, declaring that he is “utterly distraught about the pain” that he has subsequently caused his family. Ross played the part of Queen Eleanor -- Kristen Stewart's mom -- in the recent “Snow White” film.

Pattinson, 26, reportedly moved out of the home he was to share with Stewart, last week.

“Robert hoped to marry Kristen and was making preparations to spring a proposal before she admitted cheating. He had bought the house in Los Angeles to be their home and saw them staying there for a long time,”a source reportedly told British paper “The Mirror.” “Now Rob is angry – he’s left the mansion and not spoken to her since. They have exchanged heated text messages only.”

“Friends of Robert have told us that this was the woman that he wanted to spend the rest of his life with and he was actually very close to proposing when he heard about the affair,” Us Weekly’s Dina Sansing was quoted as saying.

Pattinson and Stewart met on the set of their “Twilight” series, which is set to release its final film in November.  They are reportedly scheduled to appear together in September for the MTV Video Music Awards.