Germany has been transfixed by the story of identical twins who were separated as babies, brought up by different families and reunited as adults.

The twist in the tale of Ulrike Reichenbach and Cornelia Holzbrecher is that they were brought up on opposite sides of the Iron Curtain.

Their joint memoir has been on the bestseller lists since publication in December and has invited the country to reflect on its division under communism as well as sparking a national debate on nature versus nurture.

For Ulrike, who grew up in the West from the age of 12, there can be no doubt that genes play the dominant role. “Our story is the story of the human spirit,” she said last week. “It is in our genes how we will turn out and not wholly determined by upbringing. A system cannot change people and it cannot make people.”

Separated three months after their birth by the East German orphanage where their mother had placed them - as was state policy for twins being adopted - Conny and Ulli, as they are popularly known, were raised in very different circumstances. But their tastes and habits were uncannily similar, even though they were unaware of it.

Although Ulli led a more affluent life than Conny from the age of 12, when her adoptive father, an ophthalmologist, defected to the West, she and Conny, who was raised by a plumber and his wife in the communist East, both grew up loving sport and art.

Both did apprenticeships in cooking. They passed their driving test within a day of each other. Both gravitated towards a career in event management.

The girls both claim to have felt a persistent and elusive sense of loss throughout their childhood. Conny had a doll with no name that she carried with her everywhere. When people asked her the doll’s name she would answer: “She hasn’t got a name; she’s my sister.”

Last week Ulli described a feeling of incompleteness that made her crave affection as a child in spite of the loving attentions of her parents. The feeling later dogged her relationships with men.

Both girls married young and had their first child, a daughter, at the age of 19. Both divorced and say that since they were reunited they have felt more fulfilled and better equipped as wives and mothers. Ulli has since had three more children and Conny two.

Neither Conny nor Ulli is sure why their parents decided to keep them in ignorance of each other. “For Conny’s parents it’s a decision they find difficult to talk about even today,” Ulli said.

The women were reunited in 1995 after Ulli contacted the “youth office” in the town where they were born and it gave her Conny's address.

“We greeted each other but we couldn’t speak for crying with happiness,” Ulli said of the moment they first spoke on the phone.

“We cried for five minutes and then managed to calm down and talk. Of course we wanted to know everything about each other. Every last detail. How we looked, what we liked, what we had done. It was amazing how similar we were.”

Since then they have taken every opportunity to see each other, and sometimes even their own family members cannot tell them apart. It is only the diamond nose stud that Ulli wears occasionally that gives them away.

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