"I am not going to make a shrine for Kyron in my house, but I have stuff all over my house that has his face and name on it," Kaine tells PEOPLE.
It has been exactly two years since Kyron Horman, then 7-years-old, went missing from his elementary school in rural Portland, Ore., on June 4, 2010.
His stepmother Terri Moulton Horman was the last person to see Kyron after attending a school-wide science fair.
Since then, Kaine – who split from Terri on June 26, 2010 – has spent his weekends passing out flyers and T-shirts with his son's face printed on them. Kaine has never given up hope and adamantly believes his son is alive. While he waits, he has made changes to his son's bedroom.
"My heart is with him all the time and I … wonder what he is like now. I wonder what he is into. I wonder what he enjoys," he says. "It makes me feel like I am keeping pace with him when I am updating stuff. It makes me feel like he is still there."
Multnomah County Sheriff's Office
"What is right is completely up to me. He is my son," Kaine says. "There is no playbook for how you are supposed to feel. There is no playbook for how you are supposed to heal from it. There is no playbook for what you are supposed to do. Everybody is different."
Kyron's mother Desiree Young, who was divorced from Kaine in 2003, filed a $10 million lawsuit against Terri on Friday and demand she reveal information about her son.
Police have not named a suspect in the case, or even identified any persons of interest. But after two years, Kaine, too, still believes his estranged wife has information on his son's whereabouts.
"I still believe that she is involved," he says. "I still believe that someone helped her, but we just don't know where he is at."