Farc rebels in Colombia have confirmed a boy living in foster care in Bogota is the same three-year-old who was due to be part of a hostage release deal.
Clara Rojas gave birth to Emmanuel in captivity
The rebels said Emmanuel Rojas had been transferred there for his own safety.
DNA tests had shown he was almost certainly the son of Clara Rojas, who is still being held by the rebels.
A much-anticipated release, mediated by Venezuelan President Hugo Chavez, of mother, son and a third hostage planned for last weekend never took place.
The BBC's Jeremy McDermott say the admission is a big blow to the credibility of the Farc rebel movement.
Farc had said that the planned release had been called off because of Colombian army movements in the area where it was due to take place.
Surprise and relief
Emmanuel, said to be around three years old, is believed to have been fathered by one of Ms Rojas' captors.
The elderly mother of Clara Rojas is in Caracas awaiting news
She was kidnapped in 2002 along with former presidential candidate Ingrid Betancourt.
A former congresswoman, Consuelo Gonzalez de Perdomo, had also been due to be freed.
Clara Gonzalez Rojas, mother of Clara and grandmother to the boy, said she was satisfied that Emmanuel had been found.
"This is what we least expected - personally it took me by surprise - but... we believe the tests that have been carried out are credible," she told reporters in Caracas.
Ivan Rojas, Clara's brother, said he was happy Emmanuel had been found but sad because his sister was still in captivity.
"Whenever she is free and can be with her son, that day we will say we are fully happy but for now we can't say that," he said.
"We're all obviously very surprised by the Farc's behaviour," Colombian Deputy Defence Minister Sergio Jaramillo told the BBC.
"After all, President Chavez had tried to help, even named his operation 'Operation Emmanuel', but we now know that the whole time it was clear that the Farc would never have delivered the boy because they never had him."
Colombian authorities say a malnourished boy matching Emmanuel's description was brought to a hospital in San Jose del Guaviare in June 2005 and then taken to a Bogota foster home, his real identity unknown.
President Chavez's mission came to nothing
DNA tests indicated a complete match between mitochondria in the blood of the boy - who has been given the name Juan David Gomez - and Ms Rojas' mother, Attorney General Mario Iguaran said, quoted by the Associated Press news agency.
This meant a "very high probability" that he was Ms Rojas' son, he added.
Our correspondent says the latest turn of events will not change the plight of hostages in Farc hands.
The rebels are unlikely to make any concessions and continue with their demands that hundreds of imprisoned rebels be freed in exchange for their hostages, he adds.
The Farc hold some 45 high-profile hostages, including Ms Rojas, who are considered "exchangeable".
But it is believed the guerrillas hold about 750 hostages in total, some for political leverage but many for ransom.