Jake's progress

The Chapman brothers have one hell of a reputation. More than Damien Hirst, with his smirks, and Tracey Emin, with her howls, these two, with their provocative, horrible wit, are the real antagonists of the YBA movement. Shaven-headed, leather-jacketed, accompanied by estate-style dogs and attitudes, they are also the pin-ups of this group of artists. But it's definitely a bad-boy crush, because if you want someone to brighten your day, don't pick a Chapman brother. Or so I thought.

I interviewed Dinos Chapman last year about some charity work he was involved in. He emerged from the Brick Lane mist flanked by boxer dogs and gave me a near heart attack from sheer terror, before bundling me into his lovely house, making me coffee and charming me virtually insensible. Today I am here to interview Jake, his little brother, because he has written a novel. I am exceedingly nervous. Jake is the mouthy one. He's the one who threw a Guardian lady journalist out of his studio after five minutes, telling her to 'Get out, just get the f*** out' because he didn't like her line of questioning. More of which later.

'I'm just making a little boat,' says Dinos, who is perched on a stool, fiddling with tiny bits of wood, in the middle of their large, organised Hackney Wick studio space. I tell him I'm worried that Jake will be vile. 'Oh, don't be silly,' he laughs, and then his phone rings and I am left to wander around the space while their PA tries to locate Jake.

On a series of shelves are ready-made two-inch models - heads on stakes, mutant double-headed Nazi soldiers -ready to take their place amid the grotesquery of the world the Chapmans' art inhabits. My attention is caught by an Antarctic landscape sculpture where the penguins appear to have turned nasty and are devouring - literally tearing apart - everything in their path. It is, I am told, to be called Unhappy Feet.

Jake has been found and I am led upstairs to a quiet room above the main studio but below the office, where it all looks a bit like a cool ad agency. Jake, monster that he is, offers a handshake with one hand and a cup of tea with the other. 'Hello... Sit down... Are you cold? I'm freezing. Can I just send this text? I don't mean to be rude. It is rude but I don't mean to be.'

His Staffordshire terrier Kylie (Jake was once linked to the small singer) is snuffling and scratching for attention and ends up snuggling around my leg for most of the interview. We are both, I think, grateful for the warmth because this snazzy studio is as cold as the proverbial garret. I admit that I'm concerned about his temper. 'Oh, don't be silly,' he chortles. 'But there's nothing wrong with you having to sing for your supper.' And so the tutorial begins. Jake shows enormous intellectual rigour. He will talk an idea through, flay it, dissect it and then spit it out. I don't know if he likes the sound of his own voice or if he just doesn't like to let go of a thought until it's dead - or at least disembowelled and bleeding - beneath the weight of his argument.

Like Dinos, he has never discussed his childhood or parents. Dinos was born in London in 1962, Jake four years later in Cheltenham, and they were brought up in Hastings. Their mother is a Greek Cypriot housewife and their father is a teacher turned vet. Both brothers know that because of the provocative nature of their work (when the seminal Sensation exhibition travelled to New York in 2000, the city's then mayor Rudy Giuliani branded them 'perverts' because of Tragic Anatomies in which childlike mannequins were naked, sometimes grafted together). People constantly search for a deep-rooted reason why the brothers choose this type of subject matter. Jake is unimpressed with the amateur psychology surrounding them. 'It's dirt,' he says. 'We are just two nice middle-class kids who grew up and became middle-aged artists. From YBAs to OAPs. That's what we do. You can't turn it into anything else: it's boring. But the work is interesting.' The notoriety doesn't bother him but he does enjoy the relative anonymity that tends - with notable exceptions - to go with being an artist. 'Artists just don't lead lives that are very interesting for tabloids,' he says. 'Unless you're Tracey [Emin]. Tracey's work is all about "I was raped. I was f***ed. I can't spell." And Damien sold a £50 million skull and he's worth £500 million. That's newsworthy.'

When, in late 2006, Tate Liverpool staged a mid-career retrospective of their work, Bad Art For Bad People (does that title tell us we are complicit; by looking are we taking part in perpetrating the gruesome joke?), many thought it long overdue. The Turner Prize has also eluded them, which seems a shame considering accusations of boring, obscure finalists currently being levelled at the competition (which was won last week by Mark Leckey). Brian Sewell, the Evening Standard art critic, told me that the Chapmans 'are the only artists of their generation whom we should take seriously. I think they are that rare phenomenon of people who have matured to be infinitely more important than they ever were when they were young.'

And yet their status as purveyors of immoral horror still stands. Certainly they aim to be disruptive, but shocking and sickening? It may be a sick joke but this work is really not disturbing stuff compared to, say, a contemporary horror film. 'I think you'd have to be dressed in a Shakespearean outfit to be horrified - it's so melodramatic,' says Jake. 'I think the melodrama only persists because people tell other people that it's horrific and that we're horrific.' He draws a stick man on my notepad with a dagger sticking out of his head and drops of blood dripping down. 'Now you're not going to phone the police, are you? You're not going to confuse that with me stabbing someone in the head. This is in the realm of representation and very bad representation because that doesn't really look like a man and that doesn't really look like blood. So doing stuff to a mannequin is one increment away from this. It's not the real thing. The idea of someone looking at it and having a sincere experience of unhappiness is almost Pavlovian. It could get to the point where we've teased our audience so much that we could just show them a cup and they'd start weeping.' So as long as we continue to be outraged, they will go further to outrage us with a skip and a jump and a giggle along the way. Because this does look like fun.

He has settled down with the model Rosemary Ferguson, whom he married in 2004. They live in Islington and also have two girls, aged two and three. Rosemary also has a nine-year-old daughter with the artist Barry Reigate.