With Prince William and Kate Middleton's wedding only a couple of months away, some experts say there's no time like the present to update the 300-year-old royal succession laws that are widely considered to be sexist and antiquated.

Under Britain's 1701 Act of Settlement, a male heir takes precedence over any older female siblings, and would typically leapfrog his older sisters to the throne.

If William and Kate's first child is a daughter, she would only have first rights to the throne as long as she had no younger brothers.

Many advocates say that's simply not right.

"The idea, and it's happening in quite a number of the foreign royal houses in Europe, is that if a girl is born before a boy she should automatically become queen and not be superseded by a younger brother, as would normally happen," said royal biographer Hugo Vickers.

Vickers said the current system effectively legislates discrimination –- and the sooner it's changed, the better.

"I would rather hope that if they go forward with this -- and it's a very sensible idea -- that they must do so before any little Williams and Kates suddenly start arriving because it would be a little unattractive to start moving one out of the way in favour of another," he said.

However, it might not be that easy. While the debate has surfaced again in the British House of Commons, with lawmaker Keith Vaz recently leading a debate on the subject -- the process of changing the law is complex and convoluted.

All 16 Commonwealth countries would not only have to be involved in the debate -- they would have to give their unanimous consent to such an alteration to the Act of Settlement.

Any country that has Queen Elizabeth II as head of state -- including Canada, Australia and Jamaica to name a few -- would have to agree. If the law was changed and adopted by all countries but one or two, there's the risk that different Commonwealth countries would recognize different siblings as the rightful heir, and therefore as their sovereign, Vickers said.

Still, in a statement posted on his website, Vaz said this may be the best opportunity in decades to initiate a necessary change.

"Gender equality has been the cornerstone of British society for more than 35 years. It seems only fair that this is reflected in Royal Succession rules and with the marriage of Prince William and Catherine Middleton less than 100 days away this is the right time to bring these rules in line with 21st century Britain," Vaz said.

Vaz, who has proposed his Succession to the Crown bill in parliament, said support for the legislation has come from across party lines and from other Commonwealth countries. A number of recent polls have also indicated most Britons are ready for a change, he said.

Speaking to Parliament earlier this year, Vaz said the task may be a daunting one, but is nonetheless one that must be tackled.

"Sex discrimination has been illegal in the U.K. since 1975 and those who break the law are rightly punished," he said.

"This rule attempts to bring gender equality into our succession rules."

Vaz's bill is scheduled for a second reading on May 13, 2011.

The Act of Settlement also bars Catholics from becoming king or queen, and stipulates that any royal who marries a Catholic forfeits their right to the throne.

Though he agrees it is high time to update the law, Vickers said it should be remembered that the current system has worked well.

In one case it may have kept Wilhelm II of Germany, known as the Kaiser, from the throne -- and as a result kept Britain separate from Germany's Second Reich.

Wilhelm's grandmother was Queen Victoria. Her eldest child -- Wilhelm's mother the Princess Royal -- was leapfrogged by her younger brother who went on to become Edward VII.

The Princess Royal later married Prince Friedrich Wilhelm of Prussia at 17, and gave birth to her son Wilhelm who would go on to become the Kaiser.

If the Act of Settlement hadn't been in place, the Princess Royal wouldn't have been leapfrogged by her younger brother to the British throne.

She would have been queen, and as a result when she died in 1901 her oldest son would have succeeded her.

That was the Kaiser, who by that time was Emperor of Germany, and theoretically could have extended Germany's empire to include Great Britain.

A few years later in 1914 when the Great War broke out, Britain could have been allied with Germany.

"And that may not have been such a good fit," Vickers said.