Like Izzie, Katherine’s romance has been a bit of a whirlwind. She met Josh only last year when she starred in a video for his song, "Only You." Last October Kelley described the beginning of their courtship. "At the end of the shoot, I said, 'You're gonna go eat dinner with us, and you can't say no.' So we ate, drank and just started hanging out after that," he said.

Having a musical fiancé has its perks. Josh wrote "Katie's Song" for Katherine. In an interview with People magazine in December, Heigl said of the song, "There is really nothing more romantic than that. It was one of the most thrilling and romantic things that I've ever experienced, and it makes me really like him bad."