Hooray for the new boss bros

They call it show business. But in Hollywood it's really the family business - with the Sheens, the Sutherlands and, most famously, the Fondas ruling the roost. Now, though, it's not so much the son who is rising, or the daughters, or even the sisters, but the brothers who are doing it for themselves. Because if you want to make it in movies today, you have to be part of a directorial double act. You have to be a fraternal film-maker.

Just look at the Hollywood hits. Last year it was The Matrix, made by the Wachowski brothers, or American Pie from the Weitz bros; today it's Gladiator - directed by Ridley, the brother of Tony Scott - and tomorrow it will be the movie currently twisting US turnstiles, Me, Myself and Irene, written, produced and directed by the Farrelly brothers. Such success can't be an accident. There are too many of these box-office bonanzas from brothers for it to be a matter of mere opportunity. And it's not as if these cinematic siblings just occupy one niche in the movie market. They're everywhere: Paul and Chris Weitz and the Farrellys make film farces but Alan and Albert Hughes produce scorching thrillers like Menace II Society, while the artistic high ground is occupied by the kings of American independent film, the Coen brothers, whose new movie, O Brother, Where Art Thou?, opens next month.

So what do they all have in common? And, more importantly, how has it helped them to make hit movies? To start with, what they all do is interrupt each other and finish off each other's sentences. It might not seem like the surefire way to success, but that sort of shorthand-talking is a crucial advantage when you have to share the workload on a film set. Hundreds of decisions have to be made between the actual filming and the shots being set up between takes; so you have to communicate quickly and effectively.

"I think, when you're brothers," says Paul Weitz, "you develop a common view of things - just from the shared references from childhood. So we get along."

Fraternal film-makers also hold another advantage. They not only share the workload, they can split the various functions of a director. "Larry [Wachowski] is the front man; he speaks his ideas," says Keanu Reeves, "while his brother Andrew does the visuals." And it's the same for the Farrellys. They edit their films together but on the set they split up, with Bobby at the video monitor while Peter deals with the actors. "We don't like to talk to them as two people," Peter Farrelly comments, "because they get intimidated and confused."

Within this sort of sibling system you can also be knocking heads together, shaping your thoughts from the very beginning of a film. Like the Farrellys, the Weitzes and the Wachowskis, the Coens not only direct but also write their scripts together. Working methods between scriptwriting teams might vary: the Farrellys meet five days a week at noon and always type away until six or later, while the Coens "mope around for hours with an occasional burping out of some pages". But they all go on to the set with a common vision and a good idea of what their final film will look like .

This flexibility within cinematic kinship - where roles can be changed on and off the set - is an asset that the Coens have particularly taken advantage of. Usually it's reported that Ethan produces while his more out-going, older brother Joel directs. "Joel talks to the actors more than I do and I probably do production stuff a little more than he does. But it's largely overlapping," Ethan recently revealed in an interview on the internet. "The truth," he said, "is we both direct."

Yet the credits on a Coen film clearly state otherwise. The real reason their roles are officially kept separate is the same reason why so many brothers are effective co-directors; that way, as Joel Coen explains, they keep control over their films. "It stakes out the territory we want to keep exclusively ours. Psychologically, it's important for us to realise that Ethan produces the movie and I direct, because, in a sense, we don't want another producer or another director." To protect themselves from studio interference, these movie-making brothers keep everything - writing, producing and directing - in the family.

Now a new pair of sibling directors are extending the family circle of control even further. Indeed, the Polish brothers are closer to each other than any other fraternal film-makers - they are identical twins. What's more, Mark and Michael Polish have not only written and directed their debut movie, the aptly titled Twin Falls Idaho, they also play the film's leading characters - Siamese twins who are literally joined at the hip.

"On one level," says Mark Polish, "the film could be seen as a statement of what Mike and I feel about each other. All identical twins run the risk of fusion. It could have easily happened to us." In a remark which underlines the danger of shorthand communication falling into non-communication, the 27-year-old director recalls: "When we were kids, we didn't need to complete our sentences to communicate. We rounded off our words so much that we had to be enrolled in speech therapy before we could go to school."