New details emerge...

ET has obtained a 1998 mug shot of William Balfour, a suspect listed by Amber Alert in the Hudson family slayings and also in the possible abduction of Jennifer Hudson's missing seven-year-old nephew.

Balfour, 27, is on parole and served almost seven years in prison for attempted murder, vehicular hijacking and possession of a stolen vehicle, reports the Associated Press.

His mother Michelle tells the AP he was married for "several years" to Jennifer Hudson's sister, Julia, who on Friday, according to Chicago's WBBM, discovered the bodies of her mother and brother. Balfour and Julia later separated after her and Jennifer's slain mom, Darnell Donerson, "ordered" him out of the family home last year, Balfour's mother adds to the AP.

Balfour is now in police custody being questioned in connection to the double-homicide investigation. The young boy he is suspected of abducting was not found with him, reports say. Friday afternoon, an Amber Alert was issued in hopes of finding the child.