Former Olympic champion Mo Farah revealed in an article published on Monday he was brought to Britain illegally under the name of another child to work as a domestic servant.
Farah told the BBC that he was given the name Mohamed Farah by a woman who flew him to the UK from east African country Djibouti aged nine.
The 39-year-old, whose father was killed in Somalia when he was four, said his real name is Hussein Abdi Kahin and claimed he was made to look after another family's children in Britain.
"The truth is I'm not who you think I am," he said as part of a documentary to be aired on Wednesday.
"Most people know me as Mo Farah, but it's not my name or it's not the reality.
"The real story is I was born in Somaliland, north of Somalia, as Hussein Abdi Kahin. Despite what I've said in the past, my parents never lived in the UK.
"When I was four my dad was killed in the civil war, you know as a family we were torn apart.
"I was separated from my mother, and I was brought into the UK illegally under the name of another child called Mohamed Farah."
Farah, who became the first British track and field athlete to win four Olympic gold medals, said his children have motivated him to be truthful about his past.
"I've been keeping it for so long, it's been difficult because you don't want to face it and often my kids ask questions, 'Dad, how come this?' And you've always got an answer for everything, but you haven't got an answer for that," he said.
"That's the main reason in telling my story because I want to feel normal and don't feel like you're holding on to something."
'JUST BEING HONEST'
Farah's wife Tania said in the year leading up to their 2010 wedding she realised "there was lots of missing pieces to his story" but she eventually "wore him down with the questioning" and he told the truth.
During the television programme, Farah said he thought he was going to Europe to live with relatives and recalled going through a UK passport check under the guise of Mohamed at the age of nine.
"I had all the contact details for my relative and once we got to her house, the lady took it off me and right in front of me ripped them up and put it in the bin and at that moment I knew I was in trouble," he said.
Farah eventually told his physical education teacher Alan Watkinson the truth and moved to live with his friend's mum, Kinsi, who "really took great care" of him and he ended up staying for seven years.
It was Watkinson who applied for Farah's British citizenship which he described as a "long process" and on July 25, 2000 Farah was recognised as a British Citizen.
Farah, who named his son Hussein after his real name, said: "I often think about the other Mohamed Farah, the boy whose place I took on that plane and I really hope he's OK.
"Wherever he is, I carry his name and that could cause problems now for me and my family.
"The important thing is for me to just be able to look, this is what's happened and just being honest, really."