On Sunday evening, in a statement from publicist Lisa Kasteler, the singer appealed to the public for help, offering the reward and asking any information be given to Chicago police.
"Jennifer and her family appreciate the enormous amount of love, support and prayers they have received while she and her family try to cope with this tragedy and continue the search for Julian," the statement said.
Hudson, who won an Academy Award for best supporting actress in 2007 for her role in "Dreamgirls," was in Chicago with her family during the weekend, her sister said. Hudson's publicist did not disclose her whereabouts, but the Cook County medical examiner's office confirmed she identified the bodies of her mother and brother.
An Amber Alert remained in effect Sunday for Julian, the son of Jennifer Hudson's sister, Julia Hudson. The bodies of his 57-year-old grandmother, Darnell Donerson, and 29-year-old uncle, Jason Hudson, were found in the home they shared on the city's South Side on Friday. The deaths were ruled homicides.
"Detectives are working 24 hours on this case," said Chicago police spokeswoman Monique Bond. "There's a lot of forensic evidence. We have to work the evidence and try and solve this case. Most importantly, we want to find the child."
The Amber Alert listed William Balfour, the estranged husband of Julia Hudson, as a suspect in a "double homicide investigation."
Police said they did not have a motive for the killings but called the case "domestic related." Bond said Balfour, who had been in police custody since Friday, was transferred Sunday to the Illinois Department of Corrections "based on his active parole violation unrelated to this investigation."
Balfour has not been charged in the slayings.
Records from the Corrections Department show Balfour, 27, is on parole and spent nearly seven years in prison for attempted murder, vehicular hijacking and possessing a stolen vehicle.
Corrections spokeswoman Januari Smith said Balfour would probably remain in state custody until the Illinois Prisoner Review Board looked at his case. She would not say where Balfour was being held.
It was unclear whether Balfour had an attorney Sunday, but his mother, Michele Balfour, has denied he was involved the killings or in Julian's disappearance.
Associated Press writers Caryn Rousseau and Sophia Tareen contributed to this report.