CHICAGO -- Jennifer Hudson's estranged brother-in-law has been arrested in Illinois in the deaths of the singer's mother, brother and 7-year-old nephew.

Authorities said 27-year-old William Balfour was arrested Monday at a prison where he was being held on a parole violation. Chicago police spokeswoman Monique Bond said Balfour has been released to detectives and is awaiting formal charges.

The bodies of Hudson's mother, Darnell Hudson Donerson, and brother, Jason Hudson, were discovered in October at the family home in Chicago. The body of the singer's nephew Julian King, 7, was found three days later in a vehicle on the city's West Side.

Police took Balfour into custody the same day the adults' bodies were discovered.

Balfour, who is the child's stepfather and the estranged husband of Hudson's sister, has served seven years in prison for attempted murder and vehicular hijacking.

A week after the shooting deaths, records came to light that showed he apparently had continuing problems with drugs and anger management.

Balfour was arrested on a drug charge in June and could have been sent to jail for violating his parole. But officials declined to do so, the records showed.

The tragedy came as Jennifer Hudson, who grew up in Chicago, continues to reach new heights in her career. The recently engaged Hudson won an Academy Award for best supporting actress in 2007 for her role in "Dreamgirls."

She was also featured in the "Sex and the City" movie and stars in the current film "The Secret Life of Bees," also featuring Queen Latifah, Alicia Keys and Dakota Fanning.

Her recently released, self-titled debut album has also been a top seller.