Investigators have been relentlessly searching for any shred of evidence of his whereabouts since, and insist that this won't become a cold case.
Experts from 22 different agencies, including the FBI, have followed up on thousands of tips in their search for the missing boy.
He disappeared from school June 4, and was reported missing by his step-mother, Terri Horman, when he did not come home on the bus.
Kyron's parents are divorced and have both remarried, but for the first time his father, Kaine Horman, and biological mother, Desiree Young, spoke out together Friday, united in their grief, in an interview with "Early Show" co-anchor Erica Hill.
Kaine wore a T-shirt with his son's missing poster on it, while his mother described what the past three weeks have been like for her.
"I can't even put it into words," said Young. "It's terrible. Every day that goes by, I just want Kyron home. It's been too long."
Kaine recalled the fateful morning whlen he last spoke with his son. "When I saw him that morning, I was on way my way to work. He and I talked in our front yard," said Horman. "He was out feeding our cat, heading back inside. Just gave each other a big hug, told him to have a great day at the science fair with his project, that I was proud of him for all the effort and just the amazing project he put together and to just have a wonderful day."
Kyron's family has released three never-before-seen home videos and 200 new pictures of him, in hopes they'll prompt someone, somewhere to contact police. The videos show the second-grader performing in a school play and reading to his classmates.
"He's amazing. He's kind and warm and gentle. He's very loving. He's smart. He likes to have fun. A good sense of humor. Just loves to laugh. Just a wonderful son," Kaine said of his son.
Although Kyron's stepmother hasn't been named as a suspect or person of interest, authorities have given her a second polygraph test and have distributed flyers featuring pictures of her and her Ford truck, along with questions about her movements, reports CBS News correspondent Jeff Glor.
But Kyron's biological parents stand by Terri Horman.
"I believe she's committed, as the rest of our family is, to finding Kyron. And any other information regarding that is -- the investigators are working with her and with us to help find him, so I don't really have any other comment on that," said Kaine. Young shook her head in agreement as he spoke.
Young and Kaine Horman have chosen not to speak out to the media until now because, they say, they wanted to keep the focus on Kyron. But they say they're doing it now hoping it helps the probe.
"I'm hoping that it will bring us to the end, that Kyron will come home," said an emotional Young. "You know, it's been three weeks now. And we never thought in a million years on Friday, June 4, that we would ever get to this point."
Authorities say this is the biggest investigation ever launched in the area, and while they have scaled back on searches around the school, major crime teams are pouring over tips from across the country.
Video: New Images of Missing Kyron Horman
Video: Desparate Search for Kyron Horman
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Read: Investigators Focus on Kyron Horman's Stepmom
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Read: Kyron Horman's Case Now Considered Criminal