They were found at their Chicago home, and police are searching for Hudson's missing nephew who was at the house at the time of the murders.
An Amber Alert was issued Friday evening for the missing boy.
William Balfour, a suspect in the case, is in custody and being questioned by police. As of Saturday morning he had not been charged with any crime. A police spokeswoman said detectives were talking to "a number of people in custody".
Police say Balfour is a prime suspect in the double murders of Darnell Donerson, 57, and Jason Hudson, 29.
Hudson's publicist, Lisa Kasteler, confirmed the deaths:
"We can confirm that there is an ongoing investigation concerning the deaths of Jennifer Hudson's mother, Darnell Donerson, and her brother, Jason Hudson. No further comment will be made and the family has asked that their privacy be respected at this difficult time."
Hudson, who grew up in Chicago, was featured in the recent "Sex and the City" movie, and is currently starring in the film "The Secret Life of Bees."
She won an Academy Award for best supporting actress in 2007 for her role in "Dreamgirls" with Jamie Foxx, Beyoncé Knowles and Eddie Murphy.
Related: The Secret Life Of Bees - Early Review And Movie Trailer
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