Kristina and Karissa Shannon are American glamour models, Playboy Playmates, and twin sisters. The latest news about these twin sisters is that Karissa Shannon's break-up with Sam Jones III wasn't based on a ruse after all -- because Karissa and her twin sister Kristina tell TMZ, they ARE moving back into the Playboy Mansion. Hugh Hefner must be a happy old man right now are having these two superhot girls back.