Princess Diana holds a playful Prince Harry as her older son, Prince William, looks out over the balcony at Buckingham Palace in London on June 1988. (Reuters)

It's a weird life, being a British monarch. These days, your life is all ceremony and no power, yet everything you do is scrutinized by the notoriously fickle British press. One minute you're emblematic of everything that's great about good ol' Blighty, the next you're a taxpayer-subsidized albatross, an embarrassing and gauche legacy of Britain's class system.

But there's someone for whom it's even weirder. As bad as the British kings and queens get it, their siblings may have it even worse. While sidelined by history, they are an even greater target for tabloid indignity than their more powerful relatives. These days, royal siblings have an odd position in British society, and they lead odd lives because of that.

This is relevant, of course, because on Monday, Kensington Palace confirmed that the Duke and Duchess of Cambridge (Prince William and Kate Middleton to us) will be expecting a second child. That baby, to use royal-watchers terminology, will be known as a "spare to the heir" and would be behind older brother Prince George, in line for the throne.

In historical times, a "spare to the heir" might well have led a politically important life: Some of the British royalty's most famous names came to the throne only through infighting or their sibling's untimely demise. Richard I of England, better known as Richard the Lionheart, is revered for his being king while fighting during the Crusades, even though he was originally third in line for the throne, for instance. Henry the VIII, perhaps most notorious English monarch of them all, may never have been king if older brother Arthur hadn't died mysteriously at age 15.

However, because of different political circumstances and the fact that royals are now living longer, things have changed. The last spare to become king would be George VI, who had been Prince Albert, Duke of York, until his elder brother unexpectedly abdicated to marry an American divorcee. Despite his unease about taking the throne (he was notoriously shy and had a severe stammer), George went on to become a popular king and played an important role during World War II. His ascent to the crown was recently dramatized in the film "The King's Speech."

Britain's Princess Elizabeth, left, later Queen Elizabeth II, talks to a member of the Lewisham Women's Voluntary Service, watched by Princess Margaret, in London on May 10, 1945. (Associated Press)

Since George, a new pattern has been established. His daughters, Elizabeth and Margaret, took quite different paths. While Elizabeth went on to become Elizabeth II, Queen of the United Kingdom, her younger sister would go on to become Princess Margaret, Countess of Snowdon.

Margaret's love affairs became a source of controversy. She initially sought to marry a far older, divorced man but faced opposition from the government, the Church of England and even her own sister. She eventually married a photographer (in itself, a minor controversy) and became re-embroiled in scandal when she made the unprecedented decision to divorce him in 1978, just days after being photographed in a bathing suit accompanied by a man 17 years her junior.

Margaret's reputation clearly suffered dearly as she grew older – when she died in 2002, the Guardian noted that she had a reputation for being "capable of walking away in the middle of a conversation" and "of conducting official engagements glumly and in haste."

Margaret set a precedent that Prince Andrew, Duke of York and brother to Prince Charles, current heir to the throne, followed. Andrew married Sarah Ferguson, nicknamed "Fergie," in 1986, but they separated not long after. Even before their divorce in 1996, Ferguson was known for close relationships with other men – in 1992, she was photographed topless in the south of France having her toes sucked by her Texan financial adviser, John Bryan. Andrew gained the nickname “Randy Andy” for his  relationship with a soft-core pornography actress, among others.

Andrew's problems were worse than romantic, however. Criticized for his extravagant lifestyle and friendships with dictators, oligarchs and other dubious types, he was forced to resign in 2011 from his role as Britain's trade envoy after details of his friendship with American financier and registered sex offender Jeffrey Epstein became public. It compounded his already negative image: The year before, Andrew had been left embarrassed after a tabloid newspaper reporter filmed Ferguson offering to sell access to him for £500,000 ($800,000), despite no indication that he knew of the deal.

Britain's Duke and Duchess of York at a golf tournament at Wentworth, England, in August 1995. They divorced a year later. (Associated Press)

Being further removed from the throne seems to have left Andrew and Charles's other siblings, Princess Anne and Prince Edward, more insulated from scandal, though both have had their moments: Anne became the first royal with a criminal record after her dogs attacked two children in 2002, and Edward's failed attempts to have a real career have opened him up to ridicule in the British press.

Prince Harry, the young spare to heir Prince William, exemplifies both the negative and the positive side to the role as a royal sibling. Despite a number of scandals, including smoking marijuana, dressing up as a Nazi and being photographed naked playing pool in Las Vegas, Harry's notable joie de vivre and military service seem to have endeared him to the British public: One poll from last year found that he was the most popular of all British royals, including the current monarch.

Harry's public image may well change as he gets older. One of the strange distinctions of being a "spare" is that the older you get, the more irrelevant you become: Harry drops to fifth in line for the throne when this new royal baby is born, for example.

And thanks to a slow but steady tilt toward republicanism in Britain, the role of the royalty in Britain may change even more than that in the next few decades.