Kimberly Caldwell and David Cook may have briefly dated, and rumors of on-set "Idol" romances swirl every season. But Diana DeGarmo and Ace Young are without a doubt THE first couple of "American Idol." Although the 24-year-old Diana, who was Season 3's first runner-up, and 31-year-old Ace, who placed seventh in Season 5, only recently went public with their inter-season reality romance, the couple have actually been an item for more than two years, and their relationship is both personal and professional. Not only is Diana signed to Young Brothers Entertainment, the indie record label run by Ace with his brother Ryan, but she and Ace co-wrote her new country ballad, "Good Goodbye," for the character she plays on the CBS soap opera "The Young & The Restless," a "gum-smacking mob princess with a heart of gold" named Angelina Venziano. "We live together, and we really work together," says Diana of her surprising...