The reason: Georgia-raised Sutton and Hunter Foster, key players in two of the season's hottest musicals. She's the Tony Award-winning singer-actor-dancer who's gone from virtually unknown Millie to "Thoroughly Modern Millie." He's the naive but stouthearted hero Bobby Strong in "Urinetown: The Musical."

She's 27, he's 33, the only kids in the family Foster, a non-show-biz bunch that spent much of the 1970s and '80s in Statesboro, Athens and Augusta, Ga. Mom (Helen) and Dad (Bob, retired from General Moters) now live in Orlando. Sutton and Hunter -- those are their real names -- have no idea where their talent comes from.

"It's just the two of us," Sutton says with some astonishment, "and we happen to be brother and sister, and we happen to be both on Broadway. That's sort of a universal mind-blower."

Uh-huh. And heady territory.

Hunter has been hugged and kissed by Shirley MacLaine, who sent Sutton flowers and a very nice note. Rosie O'Donnell and Reba McEntire also sent her flowers, and Julie Andrews (Millie in the 1967 movie) faxed Sutton a congratulatory note; Hunter has heard from Eartha Kitt and Salma Hayek.

Even the critics love them, mostly, calling Hunter part of a "top-notch cast . . . full of fine voices, emanating a great sense of complicity and the air of people who are having a huge amount of fun" (The New York Times) and saying that Sutton "has the pert look, the silver voice and the dazzling legwork to make an extraordinarily winning Millie" (New York Daily News).

Ticket sales back that up. "Urinetown," in its second year on Broadway, is selling 96.5 percent of its seats. "Millie," which opened in April, is filling 90.3 percent, according to Playbill Online. Both got a healthy bump after performances on the nationally televised Tony Awards in June. "Millie" won six Tonys, including Sutton's and one for best musical; "Urinetown" won three important creative awards, but Hunter was not nominated.

He was cheering for his sister and his own show, he says, and got a pretty good consolation prize: "I got to perform on the Tonys, which was great for me."

From understudy to star

Sutton, who has yet to get her medallion and has no idea where she'll keep it, puts things into perspective. "Even after winning a Tony Award, I still think, 'I hope I'll be working again.' "

Her excitement may be tempered by the facts of theater life, that constant balancing act between employment and un. Her "Millie" success, after all, came about a bit unexpectedly. The title role was to be played by Tony winner Kristin Chenoweth, who chose a TV sitcom (now failed) instead. Next came Erin Dilly, a talented woman who just didn't fit into Millie's shoes. Sutton, who'd taken the understudy role just to be part of a project she loved, was suddenly front and center and winning accolades.

So the Fosters are bona fide Broadway stars, very excited and slightly amazed. Hunter, who's performed "Urinetown" more than 400 times, is the relaxed one; Sutton, on Broadway only since April, still is seeking her comfort zone.

"I've never had this much attention," she says, brown eyes wide. "My name in the paper. My picture everywhere. . . . It's sort of my life right now instead of my job. I look forward to when I can say, 'This is what I do; it doesn't own me.' "

Still, she and Hunter know they've been lucky. Neither has had to take a day job to support the acting habit. Neither has experienced much of the "thanks-but-no-thanks" rejection so common to so many New York actors.

Luck, yes, but also attitude.

"Hunter and I have been the type of people that have taken the opportunities we've been given," Sutton says. "We've gone back and forth from playing leads to doing ensemble work, really not limiting ourselves in any category."

Hunter hit New York in 1992 with a theater degree from the University of Michigan. Before you could say "Rum Tum Tugger," he was in stripes and on the road in a national tour of "Cats." Sutton began acting professionally at age 17 with a tour of "The Will Rogers Follies," the job that got her her coveted Actors' Equity union card. She's pretty much gone from gig to gig to gig ever since.

The siblings have so many requests for their time, in fact, that they rarely see each other even though their shows are docked just a few blocks apart.

"We play phone tag a lot," Hunter says, grinning at the circumstance. "Or see each other during interviews or when relatives come to town."

It can take days, even weeks, to book an hour with either of them. Hunter finds a small pocket of time on a Friday afternoon between commitments to another project and "Urinetown" at 8. It's an athletic piece that keeps him on the move and onstage for at least 70 percent of its 2 1/2 hours.

Sutton manages a respite at a Ninth Avenue diner, after personal time with actor-boyfriend Christian Borle and before a voice lesson. When she goes on as Millie that night, she's really on, for about 85 percent of the show.

Hunter's a man in black this sticky day, from his taut T-shirt to his jeans to the circles under his eyes (too much work, too little sleep?). His drink of choice: coffee, black; sugar, a little.

He was born in North Carolina but was a Georgian by age 4 and considers Augusta (high school, the Augusta Players) his hometown.

'I remember kudzu'

Sutton, who was born in Georgia, says she's Southern at heart even though she went to high school in Michigan. Georgia is where she first experienced theater (as the top orphan in the Augusta Players' "Annie").

"I remember having a back yard and lots of trees," she says of her Georgia days. "I remember honeysuckle bushes and I remember kudzu and I remember having really bad allergies. I remember it being hot, really hot and humid. And I remember that we got to stay home from school even if there was just a prediction of snow."

Yup, that's Georgia.

Offstage, Sutton bears little resemblance to Millie. She seems younger, more introspective, maybe a little shell-shocked from all the attention. There's no makeup this day, and her hair, lighter than Millie's, is pulled back.

"There was a time they wanted me to cut my hair into a bob [like Millie's], and I said no," Sutton recalls. "I have to have my own identity and not be completely associated with Millie at all times. I'm still me, and I haven't changed. I'm a little more stressed out than I used to be and a little more tired and run down, and my priorities have been a little askew."

She's still figuring out how to balance her personal life with the responsibility of being a leading lady. And being in demand.

The lives of both Fosters can require the speed of a sprinter and the stamina of a long-distance runner. Doing eight shows in six days is the basic minimum requirement. This week Hunter has added four rehearsals and a performance of a Graciela Daniele workshop he's doing, an interview, an audition for a TV pilot and a meeting with collaborators on a musical-to-be about Bonnie and Clyde. He's writing the book.

Sutton's extracurriculars during one particular week include a voice lesson, an interview, several meetings with casting directors and a sound check at Yankee Stadium, where she'll sing the national anthem a few days later.

Battling a bronchial bug, both have missed a show that week. It's the reason Hunter passed on an offer to record a demo with Tony winner and "Mamma Mia!" star Judy Kaye and why the popular siblings reluctantly declined an invitation to sing at a 100th-birthday tribute to Broadway great Richard Rodgers.

Sharing emotional experience

Despite the many directions in which the Fosters are pulled, "Urinetown" and "Millie" remain their top priorities.

"I enjoy performing," Hunter says, "but one of the things I enjoy most is the community of people that you work with every day. It's family. When I come to work, these people that I trust and care about, and are friends with, are almost as important as the show itself. That's part of the reason we do what we do: We get to share an emotional experience with people that are really great."

Don't look for either to leave their show anytime soon.

"I've always been the type to go with whatever's going to happen," Hunter says. "I'm going to continue to do my best to try to audition and be seen for everything, whether it's film, television or stage. I'm going to continue to write. I'd really like to write a screenplay, to write another musical, just be as creative as possible and whatever happens happens."

Sutton has a similar take on the next few years. She sees herself with a house in New Jersey or somewhere nearby, and hopes "to have established a very steady career in theater and/or film and/or recording."

"Hopefully," she says, "I'll just still be working and still just loving what I do."

For more information: www.modernmillie.com/home.htm, www.urinetown.com