The actors spent about nine months together while shooting, so they say they really forged a family. "We keep in touch at Christmas and the holidays," Julie says.
When Heather lost her husband, actor Robert Urich, to cancer, her Sound of Music siblings were there for her. "They all showed up," she says. "There's no DNA here, but they're a special kind of family. I'm okay, and part of the reason I'm okay is because of these guys right here."
When the cast got to Chicago for their Oprah Show taping, they all went out beforehand for a Thanksgiving dinner of sorts. "Everybody tried to catch up so fast because we knew we didn't have that long, and questions were coming from all over the place," Julie says.
"Suddenly you just revert the 45 years," Nicholas says. "We always seem to pick up the conversation where we left off, no matter what the time has been."
The "kids" are so close, they're currently working on a new project together. "We realized that we've got this treasure trove of memorabilia that we've kept—our home movies and photos and all of the stuff—and we're doing a book, the seven kids, and answering all the questions that everybody has asked," Nicholas says. "We thought now was our chance to kind of give that back to all the wonderful fans around the world."
More from the Show
Test your knowledge with The Sound of Music movie quiz
Where are the actors who played the Von Trapps now?
Watch behind-the-scenes footage from the film