"They're all coming to my wedding, so we'll get to see each other again," Kirkpatrick told Rolling Stone in August of his former bandmates. "Everything goes back. It's like old times."
The couple, who have been dating for three years, were engaged while on vacation in Italy, Kirkpatrick told People in October 2012.
"We had a hotel room at the Isle of Capri, overlooking the Mediterranean," Kirkpatrick, 42, said. "It was one of the most beautiful places I've ever been. And it hit me: I wanted to propose to Karly. So I ran to a jewelry store, found the perfect ring and bought it.
"We were sitting on the balcony with a bottle of champagne and I put the ring in her glass," he said. "I know it sounds cheesy, but it was romantic. As soon as I asked her, she said, 'It's about time!' And we laughed. It was spur of the moment, but it was absolutely perfect."