Their family hopes an age progression photo will help solve the mystery.
The pair vanished from a family member's home in Gary.
"It is crazy. I don't understand how they could go missing for five years and no one knows anything," said La Shann Walker, a family member.
La Shann is King's grandmother and Bynum's mother.
"I wouldn't wish it on my enemy. I wouldn't wish it on anyone," she said.
Family members have said Bynum has the mental capacity of a young child and is not able to take care of herself.
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The National Center for Missing and Exploited Children provided a photo of how King might look now, as a 7-year-old boy.
Joshua Williams is King's father. He said Gary police have been silent about the state of the investigation.
"Five years. Nothing. They won't even call my phone and say 'we are still looking.' We got a new investigator on it," Williams said.
Family members have said there isn't a day that goes by they are not thinking of King and Bynum.
"You got to take it day-by-day, and sometimes I don't think I am going to make it through the day. It's hard. It's rough," La Shann said. "We can't go on like this each day, trying to live our lives and not knowing anything."
They're hoping that someone will contact police with vital information, and they will be able to reunite with the pair. The family believes they're still alive.
"I would say come forward. This is somebody's child. You would want someone to do this if this was your loved one," Williams said.
The family is going to continue to fight for answers, they said.