Two skulls taken from a grave in Metal Bridge, County Durham, belonged to two brothers who both died aged 16. The theft is believed to be part of a feud between traveller families, according to police.
The grave belonged to Levi George Price, who died in 2001 and Gareth Price, who died in 2005.
Levi Price was found hanging from a rope in a garden shed by his father, an inquest at the time was told.
His father, Sailus Price, said Levi had seemed "perfectly normal" the previous evening when he had gone out with friends.
The following morning, on February 27 2001, Mr Price, a tree-feller, went to his garden shed and found his son hanging from a nylon rope attached to a girder.
He said: "All I can think of was that he had an argument with his girlfriend the previous evening. There was nothing else troubling him."
South Durham coroner Colin Penna described Levi's death as a "very tragic story" but could not be sure he intended suicide.