Justice Toliver was fatally shot Jan. 23 in her family's apartment in Oakland's Chinatown neighborhood.
Mario Toliver Jr. turned himself in at the Oakland Police Department at 2:15 p.m. Wednesday, attorney John Burris said, KNTV-TV, San Francisco, reported.
"He is not a hardened criminal," said Burris, who had been trying for days to convince the teen to turn himself in.
Family members had said the brother and sister had gotten into an argument over Justice bleaching Mario's clothes. Burris said there was a fight, but it wasn't over laundry.
Justice Toliver was the mother of a 2-year-old, while Mario Toliver has a child who is 6 or 7 months old.
A cousin, Greg Stewart, told the TV station Friday while the brother and sister fought like siblings do, they still "loved each other," adding both teens were stressed.