LONDON — A British court has banned a 16-year-old boy from traveling to stop him from following his three brothers, who fought with militants in Syria. Two of them died there.

High Court Judge Anthony Hayden said Tuesday that to “keep this lad alive,” he should be made a ward of the court and prevented from leaving England and Wales.

The boy’s name was not released because of his age. But the judge said he holds joint Libyan-British nationality, is from the Brighton area of southern England and grew up in an “extraordinary family” committed to waging jihad.

Martin Downs, lawyer for the local council, said the boy’s uncle had been held at the US prison camp at Guantanamo Bay. Three of his brothers fought in Syria for the al Qaeda-linked al-Nusra Front.