Monaco to celebrate birth of its royal twins

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Monaco royals Albert II Charlene
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Monaco to celebrate birth of its royal twins
Prince Albert II of Monaco and Princess Charlene of Monaco pose together at the 2014 Princess Grace Awards Gala at the Beverly Wilshire Hotel on Wednesday, Oct. 8, 2014, in Beverly Hills, Calif. (Photo by Chris Pizzello/Invision/AP)
Prince Albert II of Monaco with his wife Princess Charlene, arrive at the "Monaco Red Cross Ball", Friday, Aug. 1, 2014, in Monaco. The Monaco Red Cross Ball is a charity gala evening brings together high society as well as donors from all over the world. (AP Photo/Lionel Cironneau)
Prince Albert II of Monaco's his wife, Princess Charlene, arrives at the "Monaco Red Cross Ball", Friday, Aug. 1, 2014, in Monaco. The Monaco Red Cross Ball is a charity gala evening brings together high society as well as donors from all over the world. (AP Photo/Lionel Cironneau)
From left: Queen Maxima, Prince Albert II of Monaco, Dutch King Willem-Alexander, and Princess Beatrix, pose for an official photo prior to a dinner at Palace Het Loo in Apeldoorn, eastern Netherlands, Tuesday, June 3, 2014. Prince Albert is on a two-day official visit to the Netherlands. His wife Princess Charlene, whose pregnancy was announced officially on Friday, cancelled the trip. (AP Photo/Frank van Beek, Pool)
Prince Albert II of Monaco, with his wife Princess Charlene arrive for the traditional Christmas tree viewing and present receiving session at Monaco palace, Wednesday, Dec. 18, 2013. This event takes place every years ahead of christmas. (AP Photo/Lionel Cironneau)
Prince Albert II of Monaco and his wife Princess Charlene attend the annual picnic with Monaco's citizen, Friday, Sept. 12, 2013, in Monaco .(AP Photo/Lionel Cironneau)
Prince Albert II of Monaco and his wife Princess Charlene arrive at the "Red Cross Gala", Friday, Aug. 2, 2013, in Monaco. (AP Photo/Lionel Cironneau)
Prince Albert II of Monaco and his wife Princess Charlene of Monaco wait for welcoming U.N. Secretary-General Ban Ki-moon and his wife Ban Soon-teak, at the Monaco Palace,Tuesday, April 3, 2013, during their official visit to the Principaly of Monaco.(AP Photo/Lionel Cironneau)
Prince Albert II of Monaco and his wife Princess Charlene arrive to attend the Monaco National Day gala evening in Monaco, Monday, Nov. 19, 2012. (AP Photo/Sebastien Nogier, Pool)
Prince Albert II of Monaco and his wife Princess Charlene, pose for photographers during the celebration of the 25th anniversary of French chef Alain Ducasse' restaurant Le Louis XV in Monte Carlo, Saturday, Nov. 17, 2012, in Monaco. (AP Photo/Lionel Cironneau)
Princess Charlene, left, and Prince Albert II of Monaco attend the official welcoming ceremony in Warsaw, Poland, Wednesday, Oct. 17, 2012. The Prince with wife came to Poland for a three day official visit. (AP Photo/Alik Keplicz)
Prince Albert of Monaco and his wife Princess Charlene pose during the "South Africa Night Gala", at the Monte Carlo opera,Saturday, Sept. 29, 2012, in Monaco. Johnny Clegg performed at the opera for the Gala. (AP Photo/Lionel Cironneau)
Prince Albert II of Monaco and his wife Princess Charlene arrive at the "Red Cross Gala", Friday, Aug. 3, 2012, in Monaco. (AP Photo/Lionel Cironneau)
Prince Albert II of Monaco, right, and Princess Charlene of Monaco, left, arrive for a dinner hosted by German President Joachim Gauck and his partner Daniela Schadt, both not pictured, in Berlin, Germany, Monday, July 9, 2012. (AP Photo/Gero Breloer)
Princess Charlene of Monaco walks through the garden of Bellevue Palace in Berlin, Germany, Monday, July 9, 2012. Charlene and Prince Albert II of Monaco, not pictured, were welcomed by the German President and his partner. (AP Photo/Gero Breloer)
PALM SPRINGS, CA - OCTOBER 12: Prince Albert II and Princess Charlene of Monaco arrive to attend 'Prince Albert II of Monaco's Foundation' Award Ceremony on October 12, 2014 in Palm Springs, California. (Photo by Pascal Le Segretain/AdB/French Select/Getty Images)
MONTE-CARLO, MONACO - JUNE 20: (L-R) Prince Albert II of Monaco and Princess Charlene of Monaco attend the Monaco Yacht Club (YCM) Opening on June 20, 2014 in Monte-Carlo, Monaco. (Photo by Pascal Le Segretain/French Select/Getty Images)
MONTE-CARLO, MONACO - MAY 25: Prince Albert II of Monaco and Princess Charlene of Monaco attend the F1 Grand Prix of Monaco Gala dinner at 'Sporting d' ete' on May 25, 2014 in Monte-Carlo, Monaco. (Photo by Didier Baverel/WireImage)
Prince Albert II of Monaco (2nd R) and Princess Charlene of Monaco arrive at the Hotel de Paris to attend the St David's Day gala dinner on March 1, 2014 in Monaco. Proceeds from the event are going to Princess Charlene Foundation, which helps children through sport internationally. AFP PHOTO / VALERY HACHE (Photo credit should read VALERY HACHE/AFP/Getty Images)
SOCHI, RUSSIA - FEBRUARY 07: Prince Albert II of Monaco and Princess Charlene of Monaco enjoy the atmosphere during the Opening Ceremony of the Sochi 2014 Winter Olympics at Fisht Olympic Stadium on February 7, 2014 in Sochi, Russia. (Photo by Pascal Le Segretain/Getty Images)
MONTE-CARLO, MONACO - NOVEMBER 17: Princess Charlene of Monaco and Prince Albert II of Monaco attend the Monaco Red Cross gifts distribution as part of the Monaco National Day ceremonies on November 17, 2013 in Monte-Carlo, Monaco. (Photo by Didier Baverel/WireImage)
Prince Albert II of Monaco (R) and Princess Charlene of Monaco (L) arrive for the annual gala 'Monaa' at the Monte-Carlo Sporting Club in Monaco on November 15, 2013. The Monaa is a charity gala 'Monaco Against Autism'. AFP PHOTO / VALERY HACHE (Photo credit should read VALERY HACHE/AFP/Getty Images)
LUCCIANA, FRANCE - MAY 20: AY 20: AY 20: Prince Albert II of Monaco and Princess Charlene of Monaco attend the ceremony of St Devote at Church Saint Michele on May 20, 2013 at Lucciana in Corsica, France. (Photo by Didier Baverel/Getty Images)
MONACO - NOVEMBER 19: Princess Charlene of Monaco greets the crowd from the palace's balcony during the National Day Parade as part of Monaco National Day Celebrations on November 19, 2014 in Monaco, Monaco. (Photo by Pascal Le Segretain/Getty Images)
Prince Albert II of Monaco waves next to Princess Charlene of Monaco from the balcony of the Monaco Palace during celebrations marking Monaco's National Day in Monacoon November 19, 2014. AFP PHOTO/VALERY HACHE (Photo credit should read VALERY HACHE/AFP/Getty Images)
RANCHO MIRAGE, CA - OCTOBER 11: Prince Albert II of Monaco and Princess Charlene of Monaco pose as they arrive to attend a visit to the Barbara Sinatra Children's Center on October 11, 2014 in Rancho Mirage, California. (Photo by Pascal Le Segretain/AdB/French Select/Getty Images)
BEVERLY HILLS, CA - OCTOBER 08: His Serene Highness Prince Albert II of Monaco and Her Serene Highness Princess Charlene of Monaco attend the 2014 Princess Grace Awards Gala at the Beverly Wilshire Four Seasons Hotel on October 8, 2014 in Beverly Hills, California. (Photo by Axelle/Bauer-Griffin/FilmMagic)
BEVERLY HILLS, CA - OCTOBER 08: Her Serene Highness Princess Charlene of Monaco attends the 2014 Princess Grace Awards Gala presented by Christian Dior Couture held at the Beverly Wilshire Four Seasons Hotel on October 8, 2014 in Beverly Hills, California. (Photo by Tommaso Boddi/WireImage)
BEVERLY HILLS, CA - OCTOBER 08: His Serene Highness Prince Albert II of Monaco (L) and Her Serene Highness Princess Charlene of Monaco attend the 2014 Princess Grace Awards Gala presented by Christian Dior Couture held at the Beverly Wilshire Four Seasons Hotel on October 8, 2014 in Beverly Hills, California. (Photo by Tommaso Boddi/WireImage)
NEW YORK, NY - SEPTEMBER 21: Charlene, Princess of Monaco attends the 8th Annual Clinton Global Citizen Awards And CGCA Blue Carpet at Sheraton New York Times Square on September 21, 2014 in New York City. (Photo by Paul Zimmerman/WireImage)
MONACO - JUNE 14: Princess Charlene of Monaco and Princess Caroline of Hanover inaugurate the Princess Grace Rose Garden reopening after 8 months of work on June 14, 2014 in Monaco, Monaco. (Photo by Didier Baverel/WireImage)
MONTE-CARLO, MONACO - MAY 25: (L to R) Andrea Casiraghi, Pierre Casiraghi, Princess Charlene of Monaco and Prince Albert II of Monaco attend the F1 Grand Prix of Monaco Race Circuit on May 25, 2014 in Monte-Carlo, Monaco. (Photo by Didier Baverel/WireImage)
MONTE-CARLO, MONACO - MAY 17: Prince Albert II of Monaco (R) and Princess Charlene of Monaco attend the Louis Vuitton Cruise Line Show at place d'armes on May 17, 2014 in Monte-Carlo, Monaco. (Photo by Dominique Charriau/WireImage)
Princess Charlene of Monaco attends a welcoming ceremony held as part of Montenegro's president official visit to Monaco, on May 6, 2014, in Monaco. AFP PHOTO / VALERY HACHE (Photo credit should read VALERY HACHE/AFP/Getty Images)
BEVERLY HILLS, CA - APRIL 29: Princess Charlene, of Monaco arrives at the The Colleagues' 26th Annual Spring Luncheon at Regent Beverly Wilshire Hotel on April 29, 2014 in Beverly Hills, California. (Photo by Steve Granitz/WireImage)
BEVERLY HILLS, CA - APRIL 29: Reese Witherspoon and Princess Charlene, of Monaco arrives at the The Colleagues' 26th Annual Spring Luncheon at Regent Beverly Wilshire Hotel on April 29, 2014 in Beverly Hills, California. (Photo by Steve Granitz/WireImage)
BEVERLY HILLS, CA - APRIL 29: (L-R) Actress Angie Harmon and her serene highness, Princess Charlene of Monaco, attend the Colleagues' 26th Annual Spring Luncheon at the Beverly Wilshire Four Seasons Hotel on April 29, 2014 in Beverly Hills, California. (Photo by Jason Merritt/Getty Images)
Princess Charlene of Monaco arrives at a Monte-Carlo ATP Masters Series Tournament tennis match, on April 18, 2014 in Monaco. AFP PHOTO / POOL / VALERY HACHE (Photo credit should read VALERY HACHE/AFP/Getty Images)
PARIS, FRANCE - MARCH 05: Princess Charlene of Monaco and designer Nicolas Ghesquiere pose backstage after the Louis Vuitton show as part of the Paris Fashion Week Womenswear Fall/Winter 2014-2015 on March 5, 2014 in Paris, France. (Photo by Pascal Le Segretain/Getty Images)
SOCHI, RUSSIA - FEBRUARY 09: Prince Albert II of Monaco and Princess Charlene of Monaco attend the Alpine Skiing Men's Downhill at Rosa Khutor Alpine Center on February 9, 2014 in Sochi, Russia. (Photo by Pascal Le Segretain/Getty Images)
MONACO - JANUARY 27: Princess Charlene of Monaco attends the Sainte-Devote ceremony on January 26, 2014 in Monaco, Monaco. (Photo by Pascal Le Segretain/Getty Images)
Princess Charlene of Monaco arrives for the inauguration of a coffee shop company store, on December 4, 2013 in Monaco. AFP PHOTO / VALERY HACHE (Photo credit should read VALERY HACHE/AFP/Getty Images)
Princess Charlene of Monaco inaugurates of a coffee shop company store 'Starbucks', on December 4, 2013 in Monaco. AFP PHOTO / VALERY HACHE (Photo credit should read VALERY HACHE/AFP/Getty Images)
NEW YORK, NY - OCTOBER 30: HSH Princess Charlene of Monaco attends the 2013 Princess Grace Awards Gala at Cipriani 42nd Street on October 30, 2013 in New York City. (Photo by Pascal Le Segretain/French Select via Getty Images for Princess Grace Foundation)
NEW YORK, NY - OCTOBER 30: HSH Princess Charlene of Monaco attends the 2013 Princess Grace Awards Gala at Cipriani 42nd Street on October 30, 2013 in New York City. (Photo by Daniel Zuchnik/WireImage)
NEW YORK, NY - OCTOBER 30: (L-R) Jennifer Grant, Paula Zahn, HSH Princess Charlene of Monaco, Wendy Levy and Tiler Peck attend the 2013 Princess Grace Awards Gala at Cipriani 42nd Street on October 30, 2013 in New York City. (Photo by Neilson Barnard/Getty Images for Princess Grace Foundation)
PARIS, FRANCE - OCTOBER 09: Princess Charlene of Monaco arrives at a Ralph Lauren Collection Show and private dinner at Les Beaux-Arts de Paris on October 9, 2013 in Paris, France. On this occasion Ralph Lauren celebrates the restoration project and patron sponsorship of L'Ecole des Beaux-Arts. (Photo by Michel Dufour/WireImage)
PARIS, FRANCE - OCTOBER 02: Princess Charlene of Monaco leaves the Louis Vuitton Fashion Show during Paris Fashion Week Womenswear SS14 - Day 9 on October 2, 2013 in Paris, France. (Photo by Jacopo Raule/FilmMagic)
PARIS, FRANCE - OCTOBER 02: Princess Charlene of Monaco attends the Louis Vuitton show as part of the Paris Fashion Week Womenswear Spring/Summer 2014 on October 2, 2013 in Paris, France. (Photo by Dominique Charriau/WireImage)
PARIS, FRANCE - OCTOBER 02: Princess Charlene of Monaco attends the Louis Vuitton show as part of the Paris Fashion Week Womenswear Spring/Summer 2014 at Le Carre du Louvre on October 2, 2013 in Paris, France. (Photo by Pascal Le Segretain/Getty Images)
PARIS, FRANCE - SEPTEMBER 29: Princess Charlene of Monaco attends the Akris show as part of the Paris Fashion Week Womenswear Spring/Summer 2014 on September 29, 2013 in Paris, France. (Photo by Michel Dufour/WireImage)
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PARIS (AP) - Prince Albert II and Princess Charlene of Monaco are expecting twins next month, and the first one born will be the prince's royal heir.

The palace of the Riviera principality advised citizens on Saturday that the big moment, expected in December, will be celebrated with church bells ringing.

The palace says there will be 21 cannon shots for each baby and bells tolling for 15 minutes, followed by boat horns.

Prince Albert told BFM-TV that the first child born will be heir to the throne - unless a boy and a girl are born, in which case the boy becomes royal heir.

Albert, 56, who has two children out of wedlock, married Charlene, a South African swimmer now 36, in 2011.

See photos of Kate Middleton's growing baby bump:

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Kate middleton's second growing baby bump
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Monaco to celebrate birth of its royal twins
Britain's Kate, Duchess of Cambridge meets finalist in the child champion award Georgia Alvey, right, from Cotsford Junior school, County Durham, at the Place2be Wellbeing in Schools Award at Kensington Palace, London Wednesday, Nov. 19, 2014. (AP Photo/Paul Hackett, Pool)
Britain's Kate, Duchess of Cambridge attends the Place2be Wellbeing in Schools Award at Kensington Palace, London Wednesday, Nov. 19, 2014. (AP Photo/Paul Hackett, Pool)
Britain's Prince William and Kate, Duchess of Cambridge arrive to attend the Royal Variety Performance, at the Palladium Theatre, in central London, Thursday, Nov. 13, 2014.(AP Photo/Lefteris Pitarakis)
Britain's Kate the Duchess of Cambridge attends an Autumn gala evening dinner and reception in aid of Action on Addiction at L'Anima Restaurant in London, England, Thursday, Oct. 23, 2014. Kate is patron of the charity and met charity supporters during a pre-dinner reception. (AP Photo/Justin Tallis, Pool)
Britain's Catherine Duchess of Cambridge poses for photographers with Young Wildlife Photographer of the Year Carlos Perez Navel, after the Wildlife Photographer of the Year 2014 awards ceremony at the Natural History Museum in London, Tuesday, Oct. 21, 2014. (AP Photo/Arthur Edwards, pool)
Britain's Kate, the Duchess of Cambridge, left, and Singapore's First Lady Mary Tan leave a hotel in Kensington at the start of the state visit of Singapore's President Tony Tan in London, Tuesday, Oct. 21, 2014. Singapore President Tony Tan is on a four-day state to Britain. (AP Photo/Tim Ireland)
Britain's Duke of Cambridge Prince William, center, his wife Kate the Duchess of Cambridge and his brother Prince Harry visit a ceramic poppy art installation by ceramic artist Paul Cummins entitled 'Blood Swept Lands and Seas of Red' for its official unveiling in the dry moat of the Tower of London in London, Tuesday, Aug. 5, 2014. Their visit to the work in progress installation, which currently consists of approximately 120,000 ceramic poppies and will finish with 888,246 poppies, was held Tuesday to mark the centenary of World War I. The final ceramic poppy will be placed on Armistice Day on November 11, with each poppy representing a British and Commonwealth military fatality from World War I. (AP Photo/Matt Dunham)
Britain's Prince William, right, and his wife Kate, the Duke and Duchess of Cambridge, arrive for a commemoration ceremony to mark the 100th anniversary of the outbreak of World War I at the St. Symphorien Cemetery in St. Symphorien, Belgium on Monday, Aug. 4, 2014. The cemetery was established by the German Army as a final resting place for British and German soldiers killed at the Battle of Mons. Among those buried is Pvt. John Parr of the Middlesex Regiment, the first British soldier to be killed in action on the Western Front. (AP Photo/Virginia Mayo)
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