Balfour, 27, is the estranged husband of Hudson's sister, Julia.

Authorities said at a news conference Tuesday he was charged with three counts of first-degree murder and one count of home invasion.

The triple homicide has been described by officials as domestic in nature.

Balfour was arrested on a parole violation shortly after the bodies of Hudson's mother Darnell and brother Jason were discovered in their home Oct. 24. The corpse of the star's 7-year-old nephew Julian King was found in the back of an SUV several days later.

Balfour, who has long been considered a person of interest in the case, has been in police custody since the fatal shootings on the parole violation, but was not arrested specifically for or formally charged with committing the violent crimes.

He was arrested in jail for the slayings Monday and charged Tuesday.

His lawyer Joshua Kutnick told People magazine Balfour didn't kill his in-laws and step-son.

"The delay between the crimes and his actual arrest show weaknesses in the case," Kutnick told the magazine. "This case is not a strong case against William. He is a convenient suspect."