Take two: Twins Days festival

What do almost 3,000 sets of twins do when they get together for the weekend? In Ohio, they emulate any other large gathering of Midwesterners: hold a wiener roast and an all-day chicken barbecue, and have a parade, with a few talent contests thrown in for good measure.

In every other respect, though, the annual Twins Days festival – held in the leafy, inevitably named town of Twinsburg, not far from Cleveland – is unlike anything else. Everything comes in pairs: the wizened old men in sailor hats and Minnesota Twins baseball jerseys, the young blondes with hoop earrings and identical tan lines above their strapless white tops, the old Quakers sporting conservative white shirts with vests underneath (not to mention the identical paunches).

Some twins dress exactly alike – at least for the "Double Take" parade through the streets of Twinsburg. Some don't. Some have the same hairstyle and – for the men – the same choice of facial hair; some don't. Some are identical twins, some are not. Some live together. Some are married to two sisters, or two brothers. In the more extraordinary cases, they think and talk almost exactly alike – one of them starting a sentence and the other finishing it. Or they have babies on the same schedule, and sometimes in the same gender order.

Two of the regulars are Betsy Rae and Susan Rae Geul, local girls who have been coming to the festival since it started in 1976 – when they were one-year-olds, born four minutes apart, and known as the Diersing twins.

Since then, they have married brothers, Rob and Mike Geul, in a double wedding five years ago – each had a brown-eyed daughter and a blue-eyed son, in that order. They live across the street from each other, spend much of their free time including holidays together, and work in the same restaurant, Betsy as a baker and Susan as a pastry chef.

Their father, Ray Diersing, was one of the festival's founding fathers, and it's an event they both cherish. "It's the only place you can go and ask, 'Where's your twin?' instead of people asking, 'Are you a twin?'," Susan told the local paper a couple of years ago. "It's where you can dress the same and no one gawks at you like you're a freak show."

That last part may not be strictly true. The festival has always attracted a healthy smattering of photographers and non-twins amazed by the sight of so many replicated faces and body types. One set of twins showed up this year in matching T-shirts that read, "He's a clone", with an arrow pointing to the other. Others teased their hair and placed their sunglasses so exactly alike that they could only have been doing it for the cameras.

For the most part, the twins here love to be photographed and made a fuss of. When they pose, one will often ask to change places with the other because they have an instinctive feel for whose side is whose.

The festival is not the only gathering of twins in the world, but is reckoned by the Guinness Book of Records to be the largest, with well over 2,000 pairs showing up each year. (The organisers have been itching for years to reach the 3,000 mark, but are yet to get there.)

The name of the town, of course, has a lot of do with it. Back in 1819, Twinsburg was known as Millsville – or sometimes by the even blander monicker, Township Five – when a pair of enterprising identical twins from Connecticut arrived and bought 4,000 acres of land for resale and development. Moses and Aaron Wilcox offered six of those acres to the township for use as a public square, along with a $20 contribution towards building a public school system, in exchange for just one thing – the renaming of the town to Twinsburg. Their wish was speedily granted.

The Wilcoxes were as extraordinary as any modern twins. They were lifelong business partners, held all their property in common, married sisters, had the same number of children, contracted the same fatal disease and died within hours of each other in 1827. They are buried together in the town's Locust Grove Cemetery, and their tombstone is a popular stopping-off point for festival attendees.

The festival itself started as something of a lark in 1976, the year of America's bicentennial celebrations. The organisers put on a marathon run to Cleveland, a skydiving act, and offered hamburgers and corn on the cob. A grand total of 37 sets of twins showed up.

By 1979, the festival was attracting twins from overseas – one set from Poland and another from Lebanon. By 1985, more than 1,000 sets were showing up each year and by the end of that decade the number of regulars had doubled. In 1993, the festival played host to a double wedding, but has not repeated the experience.

In recent years, it has also become a magnet for university researchers who jump at the chance to find so many twins in one place – ideal for conducting control experiments of all kinds, especially ones analysing the effects of environment versus genetics on anything from ageing to the development of skin diseases. Sandy Miller, the main event organiser – her husband Andrew sadly died just one week before this year's festivities – likes to joke that researchers can do in one three-day weekend what might otherwise take them three years.

The festival has already spawned one notable book, by the respected American photographer Mary Ellen Mark. Her research garnered some priceless stories, including one about a woman who was married to a twin, Larry Demonet, but lived with the other, David. "I cook for both of them. I do their wash. I do everything for both of them. I got two husbands!" she said. "I only sleep with one."