The tragic crash happened just before 10 p.m. Thursday.
Raihan Dakhil, the last remaining survivor of the crash, was taken off life support on Monday.
In a statement, the Long Beach Police Department confirmed the boy succumbed to his injuries at a hospital on Saturday morning.
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A GoFundMe page identified the young victim as Omar and said his parents were Raihan Dakhil and Joseph Awaida. A memorial was set up at the site of the crash Saturday, where family and friends gathered to mourn Omar and Awaida.
"They were just on the sidewalk, the whole family, and the baby Omar... It's heartbreaking," said family friend Mohammed Al Rawi.
Friends say Awaida worked at his family's auto repair shop in the area while he was studying to get his medical degree.
Police say the family, who was trick-or-treating at the time, had been run down on a sidewalk by a 2002 Toyota Sequoia. All three victims were rushed to hospitals.
The driver of the SUV, 20-year-old Carlo Navarro, was detained at the scene and later booked on suspicion of DUI and gross vehicular manslaughter, authorities said. The Long Beach resident is out on bail after it was set at $100,000.
The death of 30-year-old Joseph Awaida was announced Friday.
A statement on the GoFundMe page noted that "Joseph and his family are Muslim, and according to custom, burials are usually conducted within 24 hours of passing."
More than $175,000 had been raised as of Sunday night.
Anyone with information about the crash is asked to call Long Beach police Detective Sirilo Garcia at (562) 570-7355. Those who wish to remain anonymous can do so by calling the L.A. Crime Stoppers hotline at (800) 222-8477.