Rebecca Guinness is the archetypal New Yorker: she lives the 24/7 work-hard, play-hard culture; she has the loft, the coffee habit and the weekly manicure. She fell in love with the city's hectic charm when she came over for Thanksgiving with her American mother as a teenager and had the wildest days of her life. After college, at 21, she scraped together some money from summer jobs and emigrated.

"New York is not like any place I've ever been," she raves. "The energy is so infectious. Unlike London, which is so cliquey, closed and claustrophobic, people are kinder and more open. They take you at face value if you're nice to them. It's a lot like Ireland in that sense."

She made the rounds at America's elite glossies and got an internship as the go-to-girl and researcher at Vanity Fair before becoming a fashion assistant at Harper's Bazaar. But the city for her, she says over drinks at an East Village cafe, has been a trial by fire. Not yet 30, Guinness lives in a tiny, mid-town apartment without a TV and a revolving collection of hanger-ons and now works as a fashion assistant for style magazine Lucky.

"It's not as highbrow as Harpers or W, but it's more enjoyable. Everyone is more chilled-out and happier," she says.

Sometimes she finds the media obsession with celebrity vacuous.

"I do love the fun and frivolity of fashion, but there are times I feel disheartened," she explains, referring to the elitism and egos that cloud the industry.

"You just have to roll your eyes. It's just fashion, nobody's dying. With the big glossies, you can do some great work but they can really take over your life."

She considers the competitive nature of the city hard.

"I definitely think it harms you. People who do well here are generally pushy and ruthless. It's probably why I'm not as successful as I'd hoped to be. It's not worth trading your soul for or losing your sanity."

After vanishing outside for a cigarette with the photographer, her 27-year-old musician brother Rory reappears. He joined Rebecca in New York six years ago, when, he says, he "started a band, wrote some good songs, wrote some bad ones and had a hell's amount of girlfriends."

He says he doesn't suffer from homesickness but pines for the animals on the family farm in England.

"Being in New York, you can quickly get over not being with your pets, family or friends, but I really miss the horses. They're so graceful and gentle, you get so attached to them."

When asked about their upbringing in rural Ireland with their stepfather, the grand literary writer JP Donleavy, they are both suddenly skittish and silent, saying only that they spent their early childhood in a big, gloomy, old house in Mullingar.

Rebecca breaks the silence. "When we moved to England, we became totally different people. We changed our names, changed everything. Our parents are farmers, you know, humble beginnings. They breed event horses in Wiltshire."

Her brother, the gangly pretty boy who claimed to be shy at the photoshoot earlier yet posed like a pro, unloads his recent troubles. His band, I-Lash, broke up, and he lost his mad Vietnamese girl and his flat in one week. Now he's slumming "on Rebecca's sofa, but life is good".

They lived together before when he first arrived -- "in a shabby East Village wreck with a 24-hour atmosphere of all-night delis, shops and bars. We used to have epic parties," he remembers fondly.

"One night," he adds, "we had nearly 200 people and the floor collapsed. Finally, it got out of control to the point where the neighbourhood drug dealers came and just stole stuff, so we stopped having them."

"It turned into these communal living situations," Rebecca adds. "People came to our parties and stayed for days. People took advantage. Some more than others."

"Nothing's changed," says Rory. "Rebecca's very meek and a notorious pushover. Generous beyond her means."

"I think I just have a mothering instinct, taking on waifs and strays," she says. "I am tired of all the freeloaders living in my flat. But I don't have anyone at the moment."

"Aside from me, I'm a terrible freeloader," he says, promising to get himself a place once he returns from London, where he's going to record and visit his parents and pets.

Rebecca concedes that she has a fear of living alone. "I got a one-bedroom flat recently rather than sharing with others because I thought I've grown-up now. But eventually I have people living on my sofa, in my bed. I get terribly bored and lonely if I'm by myself."

"That's probably why you end up with these losers who are unstable," Rory tells her.

"It's true. Rory told me the other day that I have the worst possible taste in men. I've only just realised that my type is crazy. Real bastards. One of my boyfriends was psychotic and had a drug problem. But the great thing about New York is that it's so small. You can go to 17 different parties in one night."

"Sometimes it's too small, especially if there are people you want to avoid," he observes.

"One of my ex-girlfriends was friends with the owner of this naff, ultra-trendy bar. The day I broke up with her, I went there with some mates. The moment I walked in, the owner saw me and sent over her heavies. They literally threw me out into the street. American women can be scary and aggressive. Sex and the City didn't come out of nowhere. This is a terrible city for women to have relationships. If you're a vaguely good-looking guy here, you have easy pickings and can treat women however you like."

When Rory came to New York, before he became "a failed musician, he was a failed actor" doing short films, voice-overs and extra work.

"Taking acting class was one of the best things that I've done. I was painfully shy, emotionally crippled. It's helped me break out of my shell, which I seem to be drifting back into," he says half-jokingly.

Recently, he's been scraping a living as a runner on films and writing press releases for The Strokes.

"I've realised the nine-to-five isn't my thing. As an artist, it's much easier to work as a waiter or bartender. You can earn $1,000 a night. My girlfriend didn't let me bartend because she wanted me home at night," he says, before launching into a story about his first gig where his girlfriend was arrested by undercover police for smoking weed.

"I had to go on stage minutes later so I told the audience, 'My girl's been taken to prison', and then played the show.

"I've had an amazing time in New York," Rory adds, "but I don't have any illusions about where I belong. I know I'll go back to Europe."

"I'm pretty content wherever I am," Rebecca says. "You can dump me in the wilderness and I'll adapt. But I don't like how the city can trap you. New York can drive you crazy, but it's exhilarating. There's nowhere else like it."