In light of the Robsten split, we know you all need answers. Why did the couple fall apart?

Well, remember when Kristen Stewart cheated on Robert Pattinson with Rupert Sanders? Yeah? So does Pattinson. And that became a problem.

Us Weekly reports that Pattinson simply couldn't get over last summer's infidelity and used it against Stewart whenever he could. "He really put her through the ringer [sic]," a source told the mag. "Ultimately, it was like, 'Either we move past this or we don't.' It wasn't good for either of them."

Another source told the tab that the pair fought a lot more often towards the end of their relationship, and those fights got messy because Pattinson used the old "you were photographed making out with your married director while we were together" card.

"Rob always brings up the cheating scandal to Kristen," the insider said. "He hangs it over her head."

"They're both good people," a source insisted. "It was just not the right thing for either of them right now."

Initial reports said this breakup may be temporary, but with Pattinson spotted moving out of Stewart's house -- and Taylor Swift getting involved -- sources are saying now that it will probably stick.