The release of Ashya King's parents means the family's plans to get the five-year-old to the Czech Republic for proton beam therapy is back on track, his brother Naveed told ITV News.
"Progress is being made to get Ashya to the Czech Republic to get everything sorted out as soon as possible," he told ITV News in an internet video conversation.
An internet connection problem means part of this video may be difficult to understand.
The head of the police force which applied for a European Arrest warrant against the parents of Ashya King has now urged their release.
A British mother whose son's life was saved by proton therapy has told ITV that she defied NHS doctors' advice to pursue the treatment.
The parents of Ashya King said they took him out of a hospital to seek proton beam treatment which is not available under the NHS.