With five children and a punishing work schedule, Justin Chambers should look exhausted. But the 35-year-old former Calvin Klein model, who plays kind-but-surly doc Alex Karev in hit TV show Grey's Anatomy, looks pretty darned good. Though he plays the ladies' man in the show, his legions of female fans will be disappointed: Chambers is strictly a family man

Born and raised in Ohio, Chambers started his career with a series of modelling jobs in the 90s where he met his wife Keisha, a model agency booker, whom he has now been happily married to for 12 years.

The high-cheek-boned thirtysomething is one of a brood of five himself (including his twin brother Jason), and loves his role as a dad to four girls and a son.

'I'm not the Daddy that does the nine-to-five job, but it's never been bad,' he says. 'I have been a parent most of my adult life so I don't know any different. I know a lot more about raising kids than some fathers who don't see their kids except on Sunday.'

It took him more than a decade from his early modelling days before he started hitting the big time. 'I've never been popular but I've done enough work where I've been able to profit and provide and have a decent life.'

But Grey's Anatomy has put new pressures on his family life, due to long working days on the opposite side of America; Grey's is filmed in L.A. and the family lives on the East Coast.

'I have an amazing support system, my wife is a full-time mother and her parents have always helped,' he adds. 'We've been doing the whole back-and-forth thing.'

Chambers hasn't succumbed to the temptations of fame and celebrity, or even had a chance to, because his brood keeps him grounded. 'It keeps you in line, having a family. It also gives you a reason to do what you do. Kids are hard, but so rewarding,' he says.

Chambers had small TV roles and parts in films including The Musketeer and The Wedding Planner, but Grey's Anatomy has been his big break - and accelerated his pin-up status. An actor who doesn't take his job too seriously, he has a similar attitude about his former life as a major player in the modelling world, working for Armani. 'I don't look like a model in real life,' he says. 'I'd go in for shoots and they thought I was the delivery boy - but I pulled it off for a while.'

Largely thanks to the recognition he has achieved through Grey's, Chambers has also made his first big break into films with the lead role in serial murder thriller The Zodiac. Filmed on a $1 million budget, Chambers plays a detective who becomes obsessed with a series of unsolved killings in California in the 1960s and the 1970s.

'Everyone's fascinated because we are all born with a good and bad seed. That is why we are a little bit titillated by it,' he says. It's intriguing.' The actor took some inspiration for the role as detective from his parents, who both worked for the police force. 'My mum was a deputy so she worked in the jail house, and my father was on the road,' says Justin. But where he grew up, the mean streets weren't unbearable. 'It was a pretty laid-back community: a crack addict here and there but never any horrific crimes that they had to investigate.'

So what is next? 'I am looking at some cool stuff, if it's possible. But I want to stay on this show for a while, I will juggle whatever comes my way.'