March 15, 2014 -- Paul Fronczak, a 49-year-old Nevada man who recently discovered that his entire identity was false, is now closer to learning who his real biological family is and where he came from.
Fronczak is at the center of a mystery that dates back nearly 50 years, when a baby boy was stolen from a Chicago hospital in 1964. At the time, the Chicago police and the FBI launched a massive investigation to find the missing baby. When an abandoned toddler was discovered in New Jersey, who seemingly matching baby Paul's description, police and the Fronczaks thought their son had been found and their nightmare was over.
But recently, Paul Fronczak underwent DNA testing that revealed the couple who had raised him as their own was not related to him. Ever since, he has been on a mission to solve two mysteries: Who he really is and what happened to the real Paul Fronczak.
"I feel kind of like an imposter because I am still using his birth certificate. Paul is out there," Fronczak told ABC News' Barbara Walters. "I have his birth certificate. ... I want to give it to him, and I want to find mine."
Desperate to find any connection to his biological family, Fronczak sent DNA samples to three genealogy websites: 23andMe.com, familytreedna.com and Ancestry.com. The results, according to Ancestry.com, showed that Fronczak was 37 percent European-Jewish descent. It was his first indication of his real identity.
"I was raised Roman Catholic," he told "20/20." "And I'm actually Jewish, so, it's kind of cool. I have to learn a whole new religion now. I'm excited about that."
But even more exciting was that a name popped up in Ancestry.com's search that said it was a possible third cousin, so "20/20" helped arrange for Fronczak to meet his first possible blood relative, Fran Kirby.
Kirby said she had no idea Fronczak existed until she Googled him after watching "20/20's" October report.
"It's a very big deal," Fronczak said. "This is really huge. This is one step closer."
Then, Fronczak got another match on Ancestry.com for a possible second cousin. That cousin's name was Alan Fisch, a 57-year-old father from New York.
CeCe Moore, a genetic genealogist who helped Fronczak with his case, said finding a second cousin match was "substantially better" than finding a third cousin match. A second cousin could unlock the mystery of Fronczak's true identity because his and Alan Fisch's parents could be first cousins and their grandparents could even be siblings.
But then another obstacle surfaced. Fisch was adopted and, like Fronczak, was searching for his biological parents.
"After all the twists and turns and all the challenges inherent in this case already, to find that his closest match turns out to be adopted was just unbelievable," Moore said. "Incredibly disappointing."
Then, days before Fisch was supposed to see court records revealing details about his birth mother, he died unexpectedly of a blood clot. But Fisch's children and widow Randi Fisch, determined to continue Alan's search and help Fronczak with his, agreed to meet with Fronczak.
"All four kids at the same time said they wanted to honor Alan's memory and finish this," Randi Fisch told Fronczak in a joint-interview with Barbara Walters. "He was so excited to meet you."
The next step was tracking down Alan Fisch's birth mother's name, which the family was able to do with "20/20's" help. If she is found, she would be Fronczak's closest relative revealed thus far.
Fronczak's hope is that every clue brings a tragic mystery closer to being solved.
"I'm really, really a hopeful guy," Fronczak said. "I still think we're going to solve both these mysteries. ... It's going to happen."
ABC News anchor Barbara Walters and chief investigative correspondent Brian Ross are investigating the case. Do you have any tips on this case? Click here to send them to ABC News.