Antonio Yarbough and Sharrif Wilson were serving prison sentences for the 1992 killings of Yarbough's mother, sister and a close friend, whom the two came home to find stabbed and strangled to death in Yarbough's Brooklyn home.
Yarbough, 18 at the time, and Wilson, 15, were coerced into confessing, with police promising Wilson a lighter sentence if he testified against Yarbough.
The men, who said they were "slapped around" and threatened, eventually complied, CNN said.
"I was asked to come down to the precinct," Yarbough said. "Before you know it, I had this photograph shoved in my face, and I was being threatened and slapped around, and they wanted me to sign a false confession. And I wouldn't."
Yarbough was handed a 75 years-to-life sentence. Wilson got nine years-to-life.
Both were still in prison this week when they learned prosecutor who had been revisiting convictions from the time period where DNA evidence was not considered, contacted them to tell them they had been wrongly accused.
DNA taken from underneath Yarbough's mother's fingernails was identical to that of an unidentified suspect in a similar 1999 rape and slaying -- one the two men could not have committed because they were in prison.
After 21 years and seven months, Yarbough said he still couldn't comprehend he was a free man.
"I'm still going through it right now," Yarbough said Friday. "I haven't slept yet. I've been up for two days now. I have no words for it right now."