Barack Obama's half brother was denied UK visa after being accused of sexually assaulting a group of young girls in Berkshire last November.
Samson Obama was headed for Washington via Britain to attend the historic inauguration that saw his brother become the US President in January.
But he came under the scanner of immigration officials at East Midlands Airport when the hi-tech database revealed Samson had been taken into custody by Brit cops after trying to sexually attack a group of young girls, including a 13 year-old.
He was later fingerprinted and not charged before leaving the country but not without providing his details, which were recorded on the Home Office's new database of prints and biometric details.
It was alleged that it was this "sensitive issue" that came into light as he tried to step in to the British borders to pay a visit to his relatives while on his way for the swearing-in ceremony.
"This was obviously an extremely sensitive issue when it was flashed up by the database," News of the World quoted a Home Office source as saying.
"But the system is designed to flag up people who have come to the attention of the police in the UK and are then trying to return," the source added.
A Home Office spokesman confirmed Samson, one of the President's 11 half brothers and sisters by his father who had four partners, was stopped from entering the country after immigration officers detected a false document with his visa application.
Samson was believed to have reached Washington through a connecting flight from East Midlands to the US.