Reunion beckons for Nobel winner and his long lost step-sister

Another extraordinary chapter has been added to the amazing saga of Mario Capecchi, the genetic scientist who was last week awarded the Nobel Prize for Medicine.

Dr Capecchi, who carries out his research at the University of Utah in Salt Lake City, spent five years as a young child during the Second World War surviving on the streets of Italy while his left-wing, Bohemian mother, Lucy Ramberg, was in Dachau concentration camp.

After she was liberated at the end of the war she went in search of her son, tracking him down after a year to a hospital in Reggio Emilia, southern Italy. He was nine. Soon afterwards they set sail for America.

But they left behind in Europe other remnants of Ms Ramberg's private life. This week Dolomiten, a newspaper in the German-speaking Italian enclave of Alto Adige, announced they had located Mr Capecchi's long lost step-sister.

Marlene Bonelli, now 68, lives in a tiny retirement flat in the Austrian town of Klagenfurt. She learnt that her step-brother Mario was not only alive but well but an international celebrity from the television. "I knew of his existence, or rather I knew that he had existed," she said. "But we had lost track of each other. Mario is my positive star. I would like to be able to meet him."

Dr Capecchi was lucky to survive his childhood. His mother, a half-American painter, had moved to Verona to be close to her lover, an Italian air force pilot called Luciano Capecchi, and their son Mario was born in the city in 1937. But the couple did not marry – Luciano was to die during the war – and within two years of Mario's birth, Ms Ramberg had produced a daughter by another man, a Brazilian of German origins. But this relationship also showed no sign of stability, and Marlene was adopted by a railway worker called Massimo Bonelli and his wife Luigia Linder, who raised her in the Austrian town of Villach.

Meanwhile Ms Ramberg's left-wing views and unconventional friends had brought her to the attention of the Nazis, and in 1941 she was arrested and incarcerated in Dachau concentration camp. Mario had already been handed over to friends who ran a farm with a sum of money for his upkeep – but when the money ran out he was cast adrift.

Marlene's adoptive parents did not conceal her complicated beginnings from the girl. "I knew that my natural mother had been deported [to prison camp]," she told Dolomiten. "And I knew there was another child. I presumed that they were dead."

Thirty years later she met her natural father for the first time, but he also had no idea what had become of Marlene's mother and step-brother. A trip to the town of Trento to peruse her adoption papers was no more help.

Dr Capecchi was equally in the dark about the details of his European family and of any other relations he may have had. During a scientific congress in Verona in 2002 he reportedly spent a day in the city archives trying to learn more, without success.

As an adult Ms Bonelli lived in Vienna, working variously as concierge and attendant in a hospice.

She found it ironic that she had led such a comparatively humdrum life."I was the one who was most protected," she said. "The one who was put in a position of safety."

He, she supposed, was dead, but then last week she saw his face on television, read his life story in the newspapers and the truth sank in. "Mario Capecchi, Nobel Prize winner, is my brother..."