Their father, Allan, has been charged in the death of their mother, Anita.
Zak Kustok led the Wildcats to a share of the 2000 Big Ten title. Sarah Kustok is a reporter for Comcast Sports Net and played basketball at DePaul.
During Saturday night's Northwestern game, players will wear helmet stickers with the initials of the Kustok children.
The funeral for Anita Kustok is Thursday.