George Obama has a court appearance scheduled on Monday.
George told reporters from his jail cell: "They took me from my home. I don’t know why they are charging me."
He and the president have the same father, who died in a car crash in 1982.
The White House declined to comment on the case on Saturday.
Several of president Obama's Kenyan relatives went to Washington DC for his inauguration, but George was not among them. He lives in Huruma with extended family.
Media reports about him surfaced over the summer, after a magazine article said he lived in a shack and earned a dollar a day.
George Obama has called the reports insulting.
"I'm proud of how I live," he told the Associated Press news agency in an interview over the summer. "[The media] are tarnishing the family name."
He also said he was studying to be a mechanic and works with a local youth group in Huruma.
In president Obama's book "Dreams From My Father," he describes George Obama as "a handsome, roundheaded boy with a wary gaze."