Chicago police spokesman Kevin Kilmer says no arrests have been made in the deaths, which the Cook County medical examiner ruled as homicides Sunday.
According to the autopsies, Smith died of a gunshot wound to the abdomen and multiple stab wounds. Simmons died from a stab wound to the neck.
Family members have said that the couple had been waiting at home to welcome their youngest son and celebrate his release from a Georgia prison. Two sisters who are related to the couple told ABC7 they think their brother had something to do with the deaths.
"We would like to make a plea for him, for our brother. Please come turn yourself in. We know what you did was awful and terrible, but please, don't let them catch you in the street. It's just going to be more tragedy for the family," sisters Renesa Peterson and Debra Simmons said Saturday.
(The Associated Press contributed to this report.)