Mention marriage and the Royal Family, and you would be forgiven, if not justified, for being pessimistic.

Three of the Queen's children, Princess Anne, Prince Charles and Prince Andrew, have failed marriages, leaving a less than happy legacy to her fourth and youngest child, Prince Edward as he weds his long-time girlfriend, Sophie Rhys-Jones.

For years the public has indulged in the gory details of his siblings' domestic disputes. It is a tradition that has challenged the institution of the monarchy and its future role in British society.

It is also a scenario the Royal Family is keen to avoid again.

Messy divorce

Take the Prince and Princess of Wales much-publicised divorce - the most traumatic of the royal marriages.

The elaborate, fairytale wedding of the heir to the throne and the 20-year-old former children's nanny was a grand state occasion.

Thousands lined the streets of London to cheer the couple as they wed at St Paul's Cathedral.

Andrew Morton's sensational biography

Although rumours soon surfaced of unhappiness, separation seemed unthinkable.

Sara Maitland wrote in Britain's Independent newspaper: "What we were supposed to be seeing was the representation of contemporary love ... What I now believe we saw was a mortal wound administered to a body of mythology that we love even more than we love the monarchy."

Following the births of Princes William and Harry, the couple parted ways.

By then Diana was the most photographed woman in the world and regarded as one of the most glamorous. By contrast, the prince's image had sunk to an all-time low. He was viewed by the public as old-fashioned and dull.

The scandal was fuelled by the biography of the princess by Andrew Morton. Believed to have been written with the princess's co-operation, it detailed stories of the Wales's miserable marriage including the prince's affair with old flame Camilla Parker Bowles, the princess's eating disorders and her unhappy childhood.

Camilla Parker Bowles

On the BBC's Panorama programme, Diana claimed that there had been three people in their marriage. She also admitted to having an extra-marital affair herself.

Courtiers close to the prince hit back by leaking damaging stories about Diana to the press. Their marriage in the prince's own words, was now "irreconcilable". The couple finally resolved to divorce on the Queen's request.

Public debacle

Neither was Edward's elder brother, Prince Andrew, spared from having the details of his marriage break-up splashed across the pages of Britan's tabloid newspapers.

The tabloids loved the Duchess of York

Much of the blame fell on the Duchess of York for publicly displaying her activities outside her marriage.

Her romances, financial affairs, book deals and other money-making projects kept the press amused but did nothing for the Royal Family's reputation.

The "Firm", as the family is sometimes referred to, made no secret of their utter disgust for the duchess. One senior courtier describing her as "vulgar, vulgar, vulgar".

Finding happiness

Even Princess Anne, always the picture of decorum, has suffered the pain of divorce.

In 1973 she wed renowned horseman Captain Mark Phillips. But after producing two children, Peter and Zara, the relationship failed.

Princess Anne has since found love with Captain Timothy Laurence, who she married 1992.

Despite the rancour and bitterness of the royal divorces, royal couples have been praised for maintaining friendship and good relations.

The Wales's put on a show of friendship

Prince Charles and Diana proved they could act amicably when family circumstances brought them together, such as their son William's first day at school, and at his confirmation.

Although they arrived and left separately, they were seen smiling in each other's presence and were civil to each other for the sake of their children.

Princess Anne and Mark Phillips also remain on good enough terms to take joint responsibility for their children.

The Duke and Duchess of York have gone further. The Duchess still refers to Prince Andrew as her best friend. Last year, he allowed her to move back into their home in Berkshire.

Hopes set

All eyes are now on Prince Edward to be the first of the Queen's children to find happiness in marriage.

And royal watchers say that Prince Edward and Miss Rhys-Jones's marriage stands a better chance.

A very private couple

Edward has learned from his siblings' experiences and will try to maintain a low profile. As seventh in line to the throne, there is less pressure on him as a member of the royal family.

The couple also has been together for five years. This has been helpful to Miss Rhys-Jones, who is now acquainted with the royal family and its workings.

But the expectations are never far from mind. At the announcement of their engagement, questions about the failed marriages in his family came as no surprise to Prince Edward.

"Oh somebody had to bring that up, didn't they?" the prince said. "More pressure? I don't know. I think if anybody's going to get married I hope that they think that they are going to get it right."

It may not have been the outright reassurance some would have liked to hear, but there are few who are going to be willing to write off this marriage just yet.