CLICK ON PHOTOS FOR FULL GALLERY OF GUESTS
She has increasingly come to rely on their support, spending Christmas 2009 alone with them at a Swiss ski resort. Ernst, meanwhile, was pictured kissing a mystery woman in Thailand.
The press were convinced a divorce was imminent. And it would have been one of the most costly in history since he's worth an estimated £5 billion and Caroline would be entitled to half.
But she maintained a dignified silence, even appearing as a witness for her husband's defence in his 2010 court case.
A Kenyan nightclub owner accused the German aristocrat of striking him during an argument, which had taken place ten years previously, about loud bar music.
Commentators speculate that the pair have come to an agreement, allowing each to lead separate lives while being still legally married and recent reports linked him with a 23-year-old ex-dancer named Simone.
But July's nuptials will have a starry guest list, nonetheless.
Demi Moore and Ashton Kutcher could well there to celebrate with Albert and his bride. The couple were reportedly spotted at Charlene's New York bridal shower back in April with Karolina Kurkova.
Mel Gibson is also a friend, having forged a friendship with Monaco's sovereign during their joint conservation campaigns. They were seen catching up at this year's Cannes Film Festival.
Karl Lagerfeld, chief designer at Chanel, has dressed Caroline and her daughter Charlotte Casiraghi for years and is definitely going.
So too is Albert's longtime friend, Swedish model Victoria Silvstedt (above left).
It's likely Sir Roger Moore will attend. The former 007, who spends summer at his house in Monte Carlo, was thrilled about the engagement, enthusing: "It's wonderful we're going to get a new princess".
Other high profile Monaco residents include Dame Shirley Bassey and Topshop boss Sir Phillip Green.
Boris Becker should be on hand after Albert attended his own wedding in 2009.
What's not so clear is if Albert will invite some of his former flames, who include Naomi Campbell, Claudia Schiffer and Brooke Shields.
Both Charlene and Albert are regularly seen socialising with Naomi on the social circuit (above right), and the trio seem to get on well.
Away from the celeb world, there'll be many guests from the Olympic family, headed by the president of the IOC Jacques Rogge.
There will almost certainly be a place for Albert's Olympic bobsleigh colleagues (pictured below). The prince competed in five Winter Games and he is still close to Mark Thomas, a former brakesman on his team and a vocal supporter of Charlene's. He describes her as "a great people person".
"She has carried herself with great dignity throughout their courtship. They share great friendship and love. Above all they are best friends.
"She has a vibrant personality and will be fantastic for Monaco".
From Charlene's sporting past, pro swimmer Sarah Powe has been invited. The 28-year-old – who has dual German and South African nationality – shared rooms with Charlene when they both competed in events.
"She was like a big sister to me," she says.
Family of the bride and groom
- Princess Caroline of Monaco
- Andrea Casiraghi, Caroline's elder son
- Tatiana Santo Domingo, Andrea's girlfriend
- Charlotte Casiraghi, Caroline's elder daughter
- Pierre Casiraghi, Caroline's younger son
- Beatrice Borromeo, Pierre's girlfriend
- Princess Alexandra of Hanover, Caroline's younger daughter
- Princess Stephanie of Monaco
- Louis Ducruet, Stephanie's son
- Pauline Ducruet, Stephanie's elder daughter
- Camille Marie Kelly Gottlieb, Stephanie's younger daughter
- John B Kelly III , Albert's cousin and son of Princess Grace's brother Jack
- Katherine and Nicholas his children
- Chris Levine , Albert's cousin and son of Grace's sister Lizanne
- Michael Wittstock, Charlene's father
- Lynette Wittstock, Charlene's mother
Members of foreign royal families
- The Earl and Countess of Wessex
- Crown Prince Felipe and Crown Princess Letizia of Spain
- King Carl Gustaf and Queen Silvia of Sweden
- Crown Princess Victoria and Prince Daniel of Sweden
- Prince Carl Philip of Sweden
- Princess Madeleine of Sweden
- Crown Prince Willem-Alexander and Crown Princess Maxima of the Netherlands
- Crown Prince Frederik and Crown Princess Mary of Denmark
- Prince Joachim and Princess Marie of Denmark
- Duarte Pio, Duke of Braganza
- Isabel, Duchess of Braganza
- Demi Moore and Ashton Kutcher
- Karolina Kurkova
- Naomi Campbell
- Victoria Silvstedt
- Sir Roger Moore
- Dame Shirley Bassey
- Boris Becker
- Mel Gibson
- Sir Phillip Green
- Jacques Rogge, president of the International Olympic Committee
- Patrice Servelle, Sebastien Gattuso, Jean Francois Calmes and Charles Oula Siehe, Monaco bobsleigh team
- Sarah Powe, Charlene's swimming partner from the former South African team
- Sophie Edington , Austrian swimmer
- Franziska van Almsick , German swimming champ