Merah murdered three soldiers, a teacher and three pupils at a Jewish school in the south-western French city in 2012.
Another accomplice, Fetah Malki, who is believed to have provided the guns to Merah has also been sent forward for trial.
In February, the public prosecutor asked for Abdelkader Merah and Fettah Malki to face special assizes.
Abdelkader Merah, a self-confessed radical Salafist, is accused of having met his brother at "key moments" when he was planning his killing spree and of helping him steal the scooter he used.
He has not denied being present at the time of the theft but says that Mohamed had not told him of his plan.
Investigators believe Malki provided the Uzi machine-pistol and bullet-proof vest used in the killings.
Charges of participating in the theft of the scooter against a third man, Mohamed Mounir Meskine, were dropped for want of proof.