The Jan. 9 collision took the lives of Chris Amaya-Pineda, 13, and his 2-year-old brother Damian.
The crash happened as the boy's mother, Deborah Amaya, was taking them on a routine trip to their grandmother's home.
Police on Thursday said Taylor Lee Harris, 31, has been arrested and will face two counts of murder. He was being held on $4 million bail.
Investigators say Harris has a history of prior arrests and reckless driving. He was arrested at a trailer park in the Desert Hot Springs area. He also has an address listing a residence in Henderson, Nev.
The vehicle he was allegedly driving belonged to a family member, police say.
Investigators believe a driver in a silver Mercedes may have sped through a red light as it was traveling on Main and hit the family's silver SUV that was traveling on 111th.
Driver sought in South LA hit-and-run crash that left 4 injured, including 2 teenagers and toddler
Deborah Amaya and the front passenger, a 16-year-old, were injured. Chris and Damian later died of their injuries.
A GoFundMe page has been set up to help the family.