Stewart admitted to having an affair with her married Snow White and the Huntsman director yesterday (July 25), releasing a statement in which she apologised for "the hurt and embarrassment" caused to Pattinson by her "momentary indiscretion".
Speaking in the April edition of Italy's Vanity Fair, Pattinson declared that he is "not the casual-affair kind of guy" and wouldn't ever give in to temptation while in a relationship.
Asked if he would date a married woman, the Twilight actor replied: "Life is not black and white. There are married couples that never see each other. Is that marriage?
"But there's a thing I've never got: That is, why do people cheat? I can understand the impulse, but not how you can keep two relationships going at the same time for long."
He continued: "I'm not the casual-affair kind of guy. If I choose to be with someone, it's because I really want it. When I have a relationship, I'm 100% into it."
Pattinson is said to have discovered about Stewart's fling late last week and has been left "miserable, heartbroken and humiliated" by her betrayal.
Sanders, who has two children with wife Liberty Ross, also released a statement yesterday saying that he is "utterly distraught" to have hurt his loved ones.
Ross gave an interview of her own just two weeks before Sanders's affair in which she described her marriage as "amazing".
On relocating to Los Angeles from London with Sanders, she told You Magazine: "Moving here and starting a life all over again was a lot harder than I had anticipated.
"But that's why everything feels so amazing now. We rode through the really hard times and we stuck it out."
Photo gallery - Robert Pattinson and Kristen Stewart's relationship in pictures: