-- For years, Gina Lozada grew up in Long Island, New York, thinking she was an only child.
"It was lonely and I used to drive [my parents] crazy, you know, from early on, like, 'Why can't I have a brother or a sister?'" Lozada told ABC News' "20/20." "And they never really, you know, explained why."
But 29 years ago, when Lozada was 22 years old, she discovered a long-hidden family secret after her father died tragically while on a construction job.
"[He] went to work one day, had a massive heart attack and that was it. [He] never came home. [It] was devastating," recalled Lozada.
Lozada said she was inconsolable and fixed her rage on her mother, who was the only family she had left.
"I kept saying to her, 'I can't believe I have to go through this alone. If I had a brother or a sister, we could kind of deal with it together,'" said Lozada.
That's when Lozada's mother revealed that she didn't have to go through it alone.
"It was almost like she wanted to tell me something but she was cautious, like she didn't know how to say it. I was so like crazed about being alone and being upset. And she was like, 'I have to tell you something.' She's like, 'There's two of you,'" Lozada said. "[I said], 'What do you mean, there's two of me?' She goes, 'You're not alone.'"
It turned out her father was once engaged to another woman, and the two unwed 20-year-olds were expecting a baby. But when the young woman's father found out, he banished them and forbid them from ever seeing each other again.
"She told him it was a boy, but he didn't know if her father was trying to throw him off, you know, by saying it's a boy [but] it's really, you know, a girl because he didn't want my father having anything to do with it," said Lozada.
Lozada's parents then met each other and married a year later, but despite living in the same small, Long Island town as his ex-girlfriend, Lozada's parents never discussed his love child. Once she found out she had a sibling, Lozada began a desperate search to find him or her.
"My dad thought it was a boy apparently. Then later my mother heard that her first child was a girl, so for about 15 years I searched for a girl," Lozada said. "[I called] mutual friends of theirs to find out if anyone knew anything, and nobody knew anything. It was like a big hidden secret."
Eventually, Lozada finally called her father's ex-girlfriend to ask about her half-sibling.
"But then she didn't know a lot of information either. Her father took her to an attorney to sign over her rights, and she said from that minute on, never was it spoken again," said Lozada.
Through her search, Lozada learned her half-sibling was a boy and that he was put up for adoption. She also knew the month he was born in. She then reached out to investigative genealogist Pamela Slaton and "20/20."
"New York City has what's known as birth indexes and these birth indexes, and they're available at the public library on 42nd [street] and 5th [avenue]. And then I'm breaking down my list until I whittle down to people that are interesting to me, so at that point I realize that I am definitely looking at what I believe is her brother," Slaton told "20/20." "So what I did at that point is I contacted Gina and I said look, I believe I found your biological brother. I want to send you a picture of him."
While walking with her husband, she got a weird feeling when she encountered a man at the Golden Nugget casino.
"I see this person, you know, walking towards me, a man, baseball hat down, something in his hand," Lozada said.
Once the man got within a certain distance of her, Lozada said she felt "complete body chills" and "total goosebumps." "I looked at this person to say, like, 'What the heck?' And I said, 'Oh my God, that's my brother,'" Lozada said.
Lozada can be seen on surveillance tape from the casino that day just staring at the man. Though Slaton had shown her a photo of Chris, Lozada said the man looked nothing like him.
"I didn't see him and say, 'Oh he looks like the Facebook picture,' because if you had the Facebook picture and this person next to each other, they don't look anything alike," Lozado said.
Days later, with Slaton's help, Lozada called Chris hoping to speak to the man she thinks is her half-brother for the first time after a 29-year search. At first, Chris' wife answered the phone, and she confirmed that Chris was at that same casino that day.
"I don't know what I believe in. But that was something from above. That was nothing from this world. [I] never had that feeling in my life, never. And I just knew."
After hours of unanswered calls and frantic texting, Lozada finally got Chris on the phone, and the two shared personal details about each other and made an appointment to meet in person for the first time.
Lozada and Chris say they have no interest in taking a DNA to test to confirm that they are half-siblings, because they believe in their hearts that they are related.