According to the Orange County Jail roster, Eriz and Lee are both being held on a $1 million bond and are scheduled to appear in court Monday.
They are expected to be charged with murder, police said.
The arrests follow a lengthy manhunt conducted by investigators from the Santa Ana Area CHP and the CHP's Border Division Investigative Services Unit.
A reward for helping find the person who fatally shot Aiden climbed to $500,000 in recent days.
"While these arrests will not ease the pain of a mother's loss, my hope is for the Leos family to have some peace of mind", Commissioner Amanda Ray, of the California Highway Patrol (CHP), said in the statement.
CHP Border Division Chief Watson also thanked the Southern California community for its "indescribable outpouring of concern and hundreds of tips" that helped investigators find the suspects.
Aiden Leos, 6, was fatally shot in the abdomen on May 21 while seated in the back seat of a vehicle driven by his mother, Joanna Cloonan, on State Route 55 in the city of Orange. But authorities have previously said they believe a woman was driving a white Volkswagen with a male passenger.
"The Department has been in regular contact with the victim's family, and I assure you they, like us, are committed to seeing justice served", said Border Division Chief Omar Watson.
Passersby Reyes Valdivia and his wife stopped to help when they spotted Cloonan on the freeway shoulder pulling her son from the passenger side of the vehicle. She called 911 and did her best to save him, but he was losing a lot of blood. "He's only six and he was so sweet", Cloonan said through tears after the shooting. It was not clear which of the two suspects fired. It had last been seen eastbound on the Riverside (91) Freeway toward Riverside, said CHP Officer Florentino Olivera.
The reward for information leading to the arrest of a suspect or suspects has soared past $450,000.