There were unconfirmed media reports that the men being questioned Sunday night were ages 19 and 20.
Keisha Williams, the mother of five who was struck in the crash, remained in critical condition Sunday night, according to Temple University Hospital.
Giselle Zayon, a hospital spokeswoman, said Williams' condition had not changed over the last two days.
Williams, 34, and her children were selling fruit at a stand near Germantown and Allegheny Avenues around 11 a.m. Friday when they were mowed down by a Toyota 4Runner.
Three of Williams' children - 15-year-old Keiearra Williams, 10-year-old Thomas Joseph Reed, and 7-year-old Terrence Williams - died Friday. One of Williams' neighbors and the owner of the carjacked SUV were also hurt in the crash.
The city has offered a $100,000 reward for information leading to the men's arrest. The Fraternal Order of Police offered an additional $10,000 if the men are arrested by noon Monday.
The vehicle's owner, a 45-year-old real estate agent, had just wrapped up a meeting with a client when two men approached the vehicle and forced their way in at gunpoint, Clark said Friday.
They forced the woman into the backseat and one of them took the wheel and sped north to Allegheny and Germantown, Clark said. It's believed the vehicle at some point blew a tire and the driver lost control and veered over a curb into the fruit stand.
The carjackers, who were described only as an African American man and a Hispanic man, abandoned the vehicle after the crash.
Neighbors said the family sold fruit every week to raise money for their church, Mount Zion, to help turn the lot into a playground.
Anyone with information about the crash is urged to call homicide detectives at 215-686-3334215-686-3334 or the anonymous tip line at 216-686-TIPS216-686-TIPS .