Who's Grégory Villemin?
He was a four-year-old boy found drowned in the Vologne river near Docelles, in eastern France in October 1984. His unsolved death is the country's most high-profile unsolved murder cases.
Why has he been in the news recently?
French police arrested three of his relatives raising hopes of a breakthrough. The development immediately thrust the boy's murder back into the spotlight and to the top of news sites, with the smiling face of Gregory once again omnipresent.
The police arrested Marcel Jacob, an uncle of Gregory's father, and Jacob's wife in the Vosges mountains.
Ginette Villemin, half-sister to Gregory's father Jean-Marie Villemin, was also detained in the same region, police sources told AFP.
Gregory's grandparents were also questioned but were later released.
The arrests "target people very close to the heart of this case and aim to clarify certain points and to provide answers to questions we have," local prosecutor Jean-Jacques Bosc said in a statement.
"This is a giant step on the path to the truth," said Thierry Moser, the lawyer acting for the dead boy's parents.
The arrests on Wednesday were on charges of being an accomplice to murder, failing to denounce a crime and failing to help someone in danger, said local newspaper l'Est Republicain, which broke the story.
In the course of this latest probe into the case, investigators questioned around a hundred witnesses, some for the first time, prosecutor Bosc said in his statement.
They also analysed more than 2,000 anonymous letters received by those involved in the affair, including some to magistrates working on the case.
Tell me more about the case
The “Affaire de Grégory”, as it's become known, has fascinated and horrified the French public for over three decades, and inspired at least seven books on the subject of his murder.
Here's what we do know. On the evening of October 16th, 1984 Grégory's parents – Christine and Jean-Marie Villemin (pictured below just weeks after the murder) – received a chilling, taunting phone call from an unidentified person, informing them “I have taken the boy.”
After a massive police search, Grégory's body was found in the Vologne river, about 7 km from the family home in Lépanges-sur-Vologne.
The day after, the couple received an anonymous letter addressed to Jean-Marie. “I hope you die of grief, boss. Your money can't give you back your son. Here is my revenge, you stupid bastard.”
We don't know who sent the letter. But for four years before the murder, the Villemins had been plagued by anonymous phone calls, some of which they managed to record.
However, voice experts still haven't been able to identify the caller. Years later, DNA tests, (of which there have been many) on saliva traces under the letter's stamp were also inconclusive.
Are there any suspects (apart from those arrested this week)?
Yes, quite a few. Initially the main suspect was Bernard Laroche, the first cousin of Jean-Marie Villemin, but that lead reached a brutal end.
Laroche's 15-year-old sister-in-law had denounced him to police, claiming to have circumstantial proof he had murdered Grégory. Furthermore, handwriting analysis suggested Laroche had a strikingly similar signature to that found at the bottom of the letter sent on October 17th.
However, Laroche's accuser later recanted and in February 1985, a judge freed Laroche from suspicion. But the same day, a furious Jean-Marie Villemin vowed, in front of journalists, that he would kill his cousin.
Incredibly, police refused to offer Laroche protection and, true to his word, Villemin shot dead his cousin on March 29th, as he left work.
Villemin was sentenced to five years imprisonment in 1993 for the killing, and Laroche's widow, Marie-Ange, successfully sued the French state in 2002, for their failure to prevent Bernard's death.
Does it get any worse?
I'm afraid so. In 1985, local suspicions began to turn to Christine Villemin, Grégory's mother. She had been seen in a post office on the day of the murder, and cords identical to the ones used to tie up Grégory were found in the basement of the family home.
Further handwriting analysis also seemed to implicate her, and she was held under suspicion in July of that year, before being released. A judge eventually took the rare decision to issue an order forbidding her prosecution, which largely served to clear her name.
What's happened since then?
There have been several rounds of DNA testing and voice analysis checks, all of which have promised to reveal the identity of Grégory's killer, but all of which have disappointed.
On April 16th 2013, French daily Le Parisien revealed that traces from the cords used to bind Grégory would be tested and compared with DNA samples from 10 individuals interviewed over the years, as "persons of interest" in the case.
Then it was revealed that the tests had shed no further light on the killer's identity.
But this week's arrests are a new twist.
There may be more twists and turns to come, however unlikely, as Gregory's parents live in hope of police one day finding their son's killer.