The genetic stock-taking is over and we can leave the family fold

If wise men are to be believed, shortly after nine o'clock tomorrow morning there'll be a mighty rushing of tongues and a vast exhalation of breath across the land. The noise will be Britain's workers heaving a collective sigh of relief as their offices re-open after two weeks. And the word on every lip will be: "Thank God, at last that's all over."

No doubt there are a few oddball adults, as well as a great many schoolchildren, for whom Twelfth Night and the return to work will come all too soon. But the general perception of the Christmas and New Year break is of a long dark night of the soul. The press chips in with reports of domestic violence - patricide, infanticide, abandoned babies, fits of claustrophobia, outbreaks of room rage. In every column you read, there's the same flip platitude: that we can't stand our own families.

Yet parents and children ordinarily spend vast tracts of time together without wanting to kill each other, and the return to work after the long break in the summer is often accompanied by feelings of regret rather than relief. Nor, surely, did the enforced midwinter break used to seem such an ordeal. Why does it now? There are the obvious explanations. It's a much longer holiday than it once was: with sleigh `n' holly motifs dominating the shops by October, seasonal parties being held in mid-November, and businesses winding down by mid-December, the build-up goes on and on. Once Christmas finally comes, the days are short, the weather is cold, and there's nothing to do but watch Robin Williams films on television. If you've the resources, you can escape to warmer climes, as the Blairs did last week, or to colder ones, where there's skiable snow. But you'll be be made to feel guilty if you do. The ideology of the break is purist: the pressure is to sit around for days with kith and kin, or, even more challengingly, with the in-laws.

Here, surely, is the deeper source of the problem. Christmas sanctifies the family: it puts a halo round the child, and a gentle gleam in the adult eye. But most families are dysfunctional, or scattered, or simply don't conform to the season's image, that unholy mix of Bethlehem and Dickens. The Christmas Day edition of Men Behaving Badly was one long joke about the failure of its protagonists to have the kind of festive experience (all holly berries and smiling togetherness) that books and films had told them they should be having. It wasn't very funny, but its premise was easy to identify with - no wonder it had more viewers than any other programme over the period.

Traditionally, the midwinter break is a gathering of clans. Extended families are reeled in for a kind a genetic stock-taking. This annual ceremony reminds us what our relations look like, and brings us face to face with our family traits. It's supposed to be a strengthening experience, and a heartening one. Instead of feeling solitary, we're shown that we're part of a sustaining network of blood ties. Hosting such gatherings over a meal is a rite of passage, something you do when you reach a certain age and have acquired the necessary culinary skills and a spacious enough oven. It's still a source of pride and competition: "We had 15 for Christmas lunch." "Oh, we had 23."

Midwinter feasts and family gatherings are part of most cultures, not just the Christian, which suggests there's a deep and ancient need for the process they enact. But the idea which underlies them - the prevalence of blood ties, alongside which the ties we form through school, work and home are supposedly weak and random - is not a premise we willingly recognise as citizens of secular, atomised societies. Indeed, the opposite view is more common: that we consciously choose our friends, whereas the family we're born into is an accident. Being told how we've got aunt Sophie's nose, or have inherited uncle Dick's famous short temper, may not seem relevant or important, or, if it does, may not be at all welcome. Blood is supposed to be thicker than water, but it isn't pleasant to drink - indeed we can only tolerate it once a year (or at weddings and christenings) when diluted by champagne.

Emotionally, perhaps, many of us still subscribe to an older view of the family - feudal, Victorian or whatever. Intellectually, in the West, we're Modernists, aspiring to a less oppressive model. In the art and literature that ushered in the 20th century (Joyce, Picasso, TS Eliot, Ezra Pound, Wyndham Lewis), the family is seen as the net which men and women must fly free of in order to become themselves. The true Modern, it's suggested, must move away and forge a new life, not heeding the call of parents, children and relations; the only ties worth forming are with kindred spirits, not with kin. Such ideas have seeped into the individualist ethos of our century, which tells us we're essentially on our own. We may be swimming in a gene-pool, but we don't want to know too much about it. We like to pretend we're self-invented. Hence our resentment of the family occasions which remind us that we're not.

Perhaps that's what makes Mrs Doubtfire a staple Christmas film: not because it's a topical story of a kicked-out father trying to get back in with his kids, or because it's comic (faintly) to see Robin Williams dress up as a woman, but because it taps a common fantasy. Many of us would like to walk into our families in disguise and be accepted for what we are, inherently, rather than being trapped in a given role of father, daughter, grandparent or whatever. But such stuff only happens in movies.

In theory, of course, kinship gatherings round Christmas and New Year serve a vital function in a society as mobile as ours, where it's common for members of a family to extend widely across and beyond their place of origin, rather than living in each other's pockets. They're homecomings, and without them there's the risk we'll forget our backgrounds and our relations altogether. But modern technology provides us with alternative means of staying in touch. There's phone and fax and e-mail. There are photographs. There are word processors on which, if you're tasteless enough, you can compose and print out for a hundred distant cousins those excruciatingly self-congratulatory round-robins of the year chez vous ("In June, Jeremy passed his paragliding exam with flying colours!" "Mum has been a little subdued since the hip replacement op, but the doctor says she's looking remarkably chipper for someone with so few of her own body parts left!"). They'll be making round-robins on video soon. There are many ways of catching up without having to do it in the flesh.

But getting together for a few days is the only honest way. If it's an endurance test, that's because you can't get round the fact that here are your flesh and blood. These fathers, grandmothers, uncles, aunts and cousins go back a long way. We know about the skeletons in their closet, because they're our skeletons, too. What we see of them, and of ourselves, may be embarrassing and unedifying, indeed so visceral and scary that we want to run straight back to work. But they tell us something we won't learn in the office, or at dinner with friends, where the talk is nicely neutral (politics, religion) and we can play at being people we're not.

Our families aren't the whole truth about us. But they're an unavoidable reminder of where we came from and who we belong to. Which is why the ritual ordeal of Christmas and New Year will go on being necessary for some time yet.