Foued Mohamed Aggad went to Syria with his brother and a group of friends at the end of 2013, according to a source close to the investigation.
Most of the others were arrested in spring last year upon their return to France but Aggad stayed on in Syria, the source said. Ninety people died in the Bataclan attacks on November 13.
The two other bmbers have been identified as Omar Omar Ismail Mostefai, 29, and 28-year-old Samy Amimour. Aggad was identified at the end of last week after his DNA was matched with those of his family members, the police source said.