For a sign of the times, look no further than the Windsors

The royal children - Princes Harry and William, Princesses Beatrice and Eugenie - looked thoroughly miserable on the snowy slopes of Klosters earlier this week. They may have looked like that simply because their ears were cold or they were fed up with the intrusive photographers, but it is more likely that they looked miserable because they are miserable, just like any other children whose parents have split up.

Unbelievable as it would have seemed even 10 years ago, all the Queen's grandchildren now come from broken homes: Princess Anne, divorced and remarried; Prince Charles, separated, acrimoniously; Prince Andrew, separated, more amicably but with no apparent prospect of living under the same roof as his wife again.

It is revealing to compare the frowning, twisted faces of today's four royal children with the limpid expressions of the young Princess Elizabeth and her sister, Princess Margaret Rose, in the formal, soft-filter portraits taken 50 years ago. How innocently they gazed into the camera lens: secure, trusting, unperturbed.

King George VI's daughters could rely on the deference and discretion of court photographers such as Cecil Beaton, summoned to the Palace to commemorate a birthday or a forthcoming royal tour. On public occasions their picture would be taken from a respectful distance: two demure little figures in matching coats and velvet collars, with the white gloves, white socks and button-up shoes that they wore until well into their teens. No question of being harassed or hustled by photographers.

This reticence on the part of the press signified an attitude towards royalty that has almost vanished. This is reflected with quite uncanny clarity by the difference in the faces of the little princesses then, compared with those of today's royal children. From the contrast between their expressions - guileless and confident on the one hand; insecure and anxious on the other - can be deduced the social upheavals that have taken place during the intervening years.

The crystal-clear symbolism of this transformation is the best answer to a question often posed, not least by readers of this newspaper. Do we - the media - have any right to report royalty's domestic upheavals, their private activities and, above all, those of their young children? Readers write letters of protest to the Editor when such articles appear in this newspaper. If ever I broach the topic, they write directly and often angrily to me. These readers' opinion is clear and insistent; they believe we have no such right. So why does the media disagree?

For every one person who writes to protest, there are many more who avidly scan the pictures and devour the stories. A subsection of the press has grown up devoted entirely, usually effusively, to the Royal Family. In writing about the royals, we feed a ravenous public appetite - and readers who are bored, offended or repelled by such journalism can ignore it. That is the usual answer: market forces must prevail.

But there is a better reason, and it explains why this newspaper has gradually modified its original policy of not writing about royalty except in the briefest, most factual terms. We can trace, through the emotional upheavals of the Queen and her relations, a surprisingly accurate graph of the history of family life over the past half-century. We have moved from the patriarchal family to one that expects equality between the sexes.

Just as today's young wives no longer feel fulfilled by a purely domestic and nurturing role, so also princesses, even non-royal ones, insist that they have rights and not just duties; most crucially, the right to emotional fulfilment and private happiness.

The model of family life has broken down, and is being painfully re-assembled. The Prince of Wales, his attention-seeking wife, and their troubled children are merely playing out in the public spotlight a conflict that is taking place in millions of anonymous marriages.

How will they resolve it? We wait agog, hoping their solution holds clues for us. We look at the distressed faces of their "privileged" offspring as they line up in the snow on a skiing holiday at which only one parent accompanies them, and we cannot disguise the truth from ourselves. Fighting parents inflict damage.

The Royal Family is an ordinary family writ large. That has always been its attraction. People with few family ties of their own, or whose family is scattered, can turn to the royals for a surrogate. Their relationships are as familiar as our own family tree. They provide a universal topic of conversation, a frame of reference, and offer proof that, even though they live in bigger houses, wear better clothes and take more glamorous holidays, they are as prone as the rest of us to making mistakes - and to the guilt and misery that ensue. Probably they always were; but a deferential press drew a veil over all that.

The Royal Family has always been not only the nation's figurehead but also its mirror. When we were a dignified and imperial nation, it was grave and remote. When we were hedonistic, it was frivolous and dissolute. Today it symbolises, as faithfully as ever, a society reinventing itself, discarding old structures and trying out new ones. This is not something the royal children can be expected to grasp, nor their parents to sympathise with; but we learn a great deal about ourselves by watching them - and, incidentally, tend to feel better about our own failures and shortcomings.

Ruth Dudley Edwards' s column will appear on Monday.