Paul McCartney and his third wife Nancy Shevell celebrated ten years of marriage on Saturday, and the former Beatle marked the occasion by sharing a rare photo of the two of them together.MORE: Sir Paul McCartney moves fans with very rare family photoIn the snap, Paul, 79, could be seen smiling at the camera while Nancy, 61, rests her head on his shoulder. Posting the photo to Instagram, he captioned it: "10 beautiful years together.