Friends are no substitute for family for Patrick Dempsey.

The actor declined his invitation to Grey's Anatomy co-star Katherine Heigl's wedding in favor of spending the holidays quietly with his family.

Katherine Heigl, 29, is set to marry singer Josh Kelley, 27, on December 23. Patrick won't be on hand, but he's thrilled for his co-star.

"I am so happy for her," he tells Entertainment Tonight. "I've never seen her so happy. He's a great guy, too, and they are a great couple."

Patrick Dempsey is looking forward to the role of dad this holiday season.

Patrick Dempsey, 41, who in addition to Grey's Anatomy is lighting up the big screen in this holiday season with Enchanted, will be spending the holidays with wife Jillian, daughter Tallulah, and 10-month-old twins Darby and Sullivan.

"It's the first Christmas with the boys. They'll be walking by then, so we're all very excited," Patrick Dempsey said.

Dempsey might be a no-show, but Grey's Anatomy will be represented at the wedding by castmate T.R. Knight, who will be a Heigl "bridesman."

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.