Sibling rivalry has jeopardised an alarming number of fraternal enterprises from the Mughal Empire to the Borgias and the Gucci business. So it comes as a relief that, having been declared the world's best restaurateurs after years of hovering in the wings, the Roca brothers have devised a foolproof system to stop them fatally falling out.
"If there is a difference of opinion and it's a case of two against one, the minority wins," explains Joan, the eldest brother and, as head chef, the one on whose shoulder the glory nominally rests.
"It's inverted democracy," explains Jordi, the baby brother whose extraordinary desserts have arguably played an even bigger part in elevating El Celler de Can Roca from tiny Catalonian gastropub to a restaurant now so sought after that, with all tables committed for a year ahead, the booking line is only open for one hour a month.
"That's the principal effect of being voted number one in the World's 50 Best has had on our business – extending a waiting list that was already several months long," sighs Joan, in London for this week's Restaurant Show, where he divulged a few trade secrets to British chefs.
Earlier this year, El Celler de Can Roca made it to the top of the prestigious list for the first time, knocking Denmark's celebrated Noma off the top spot it had occupied for three years.
Neat and modest in a navy blazer, with none of the flamboyance or visible ego associated with today's crop of award-laden celebrity chefs, the 49-year-old is only too ready to credit his brothers with the transformation of the family fortunes, via the evolution of their own bravura restaurant just steps from the simple café where their parents have been cooking for 50 years.
"Josep has an amazing nose, which gives him the power to match wines you might not have thought of perfectly with food, and since Jordi joined us, there has been an exponential explosion of creativity," says the chef, who feels he has picked up at least as much inspiration from his "crazy" little brother as from his early mentor, Ferran Adria of El Bulli.
"He has influenced chefs all over the world, but Jordi's genius is just for us," he says, chuckling with satisfaction. And there's no question of relegating to the dessert station the 35-year-old pastry chef, who still hasn't forgiven his big brothers for stealing his table football to stave off boredom in the early days when, a decade too early for Jordi's input, they were sitting in an empty restaurant with few clients: "The candied olives served at the start of the meal are also a Jordi creation," admits Joan.
Had the kid he thought was destined to be a rock star never surprised everyone by donning an apron, Joan wonders if he would have had the inspiration to take the traditional Catalonian dishes his parents have cooked the same way for half a century and mess about with them – such as the calamari his mother simply fries, while Joan chops some raw into a tartare and tosses others in featherlight tempura batter to serve with a light, lemony sauce.
"And before Jordi joined us, my idea of 'mar y montana', another traditional dish evoking sea and mountains, was to serve lobster simply cooked with mushrooms. Now I take an oyster and pair it with a distillate of earth I use to make a sauce that tastes of soil – it's delicious, I promise you."
The Michelin-starred chef suspects his parents think he is still playing around with mad experiments the way he did at the age of 10, when his mother was so amused by his early efforts at paella-type rice assemblages, she hand-sewed him his own chefs' jacket. "They haven't taken a single idea from us," he admits. "But we have never tired of what they do. We go over to their place and eat there every single day, because no one can make the dishes they cook as well as they can."
So you won't find Joan attempting an escudella, the Catalan stew with meatballs his mother has perfected, though he does make an avant-garde take on her pa amb tomaquet – country bread roughly rubbed with tomato, on to which Mama Roca slaps a charcoal-grilled lamb chop. Joan's modern evolution is to flavour one of his loaves with roasted tomatoes – and to celebrate the bread itself by casting a sliced loaf in aluminium on which to serve some of the restaurant's edible treats.
When I chat to Joan's brothers, who have stayed in Spain, Jordi boasts: "I am the one who brought playfulness and transgression to the partnership" and Joan's signature truffle bonbons and suckling pig with razor-sharp crackling are the dishes foodies faint over.
Josep, the quietest Roca, who as well as running a seamless front-of-house has built a 30,000-bottle list for the restaurant, says: "Even as a child, I was immersed in liquid, always jumping into puddles. And when at 12, before Jordi was born, I jumped into a well, mistaking it for another puddle, it was Joan, then 14, who pulled me out by the hair.
"I was the naughty and playful one in those days, Joan always protective and responsible. Later, I remember pulling Jordi's buggy – and that buggy sometimes serving as a goal. We used to play football even in our parents' bar, diving between the clients and using two chairs to mark the goalposts."
From such an obsession grew Jordi's fanciful dessert dedicated to the beautiful game, in which fans are invited to take their own journey through an edible football pitch with mini-meringue and macaroon balls, while egged on by a crowd roaring through an implanted iPod.
But despite their preoccupation with reliving family memories in their food, the Roca brothers are not as inward-looking as many other lauded Spanish chefs – Joan has still not got over the discoveries he made in Korea. "They have an absolutely amazing way of fermenting garlic, which we have adopted in the restaurant, and we now make our own kimchee."
It seems unlikely that these pungent additions from Asia are what the punters are queuing a year to taste, but it does knock your socks off to hear Josep relate that since winning the big global accolade in April they have given three people the job of just saying no to those pleading for an earlier table.
"Jordi may have his Willy Wonka-type ice-cream parlour, but more tables at El Celler, or another branch so we can shorten the waiting list? It's never going to happen," says Joan, suddenly playing the authoritarian big brother.
It seems fitting that Joan, before leaving London, presented the "National Restaurant of the Year" award to Tom Kerridge, another gastropub owner whose Michelin stars have lengthened his own waiting list at the Hand And Flowers by several months.