Now, a year later, both Forrest and his wife, Ruzan, are speaking out about life with their son, Leo.
"He's generally a very happy kid," Forrest of Auckland, New Zealand, told ABC News Tuesday in an exclusive interview. "He's got a sense of humor ... in many ways he's not really different than a lot of other children. He's got a lot of challenges, but to bring out the best of him you have to work with him differently than you would do another child."
After the news sank in, Forrest held Leo for the very first time: "They took me in to see him and I looked at this guy and I said, ‘He's beautiful -- he's perfect and I'm absolutely keeping him,’" he said last year.
Forrest was living in his Armenian wife’s home country where she presented him with an ultimatum: Put the child in an orphanage, or she would leave.
He chose Leo and decided he would return to his native New Zealand, where he said they’d receive support from loved ones. Ruzan Forrest filed for divorce.
Now, he told ABC News Tuesday, "It was pretty clear that the main things were cultural and huge pressure. About three-and-half weeks later, Ruzan got in touch with me through a friend and we ended up having a candid conversation through Skype. I finally agreed to meet her and she held little Leo for the first time.”
"Before this, she had no idea what Down syndrome really was, or that there was hope," he added. "The doctors had told her Leo would never learn to walk, or talk or feed himself."
Leo was born in Yerevan, Armenia, but Forrest moved to New Zealand where he said they'd receive support from loved ones.
Ruzan Forrest, 30, told ABC News Tuesday that she felt the "world was against her" after her husband had shared their story globally.
"I read all the comments and there were some positive comments, but now when I look back, [they'd say] 'Why would you leave your child?'" she said. "I didn't like the feeling, it was really bad. I thankfully forgot about it. I am very grateful my family gave me a chance because I don't know what I would do without them. It made me really happy."
Samuel Forrest, who at the time was working as a freelance business contractor, enlisted help on his GoFundMe page, titled "Bring Leo Home"
The Internet quickly rallied, raising over $500,000 (U.S.) for little Leo and his dad, after Forrest's Feb. 5, 2015, interview with ABC News.
The fundraiser was at 4,000 Australian dollars and then "I woke up in the morning and it was rolling over like a speedometer," Forrest said. "...[It] was a big shock."
The story was soon recognized by media platforms all over the world and Forrest received 18,000-plus messages from strangers, he said.
"The bulk of it was positive, then there was this huge negative story about Down syndrome, that the child should've been killed at birth," Forrest recalled. "There was a nasty underbelly, [but] I'd say most of it was ignorance.”
During the media frenzy, Ruzan took to her Facebook page in an effort to defend her actions.
"Sam has never suggested joining him and bringing up the child together in his country," Ruzan wrote in 2015. "Neither did he tell me anything … The only thing he kept saying was that he didn't want us to separate, whereas my question what we should do always remained unanswered."
Shortly after the couple reconnected through Skype when Leo was about a month old, Samuel and Ruzan reconciled. Forrest says she canceled the divorce before it was finalized and moved to New Zealand to live with her husband and son.
"She’s adapted to Leo’s therapy programs and she’s turned out to be a wonderful mother," he added.
Forrest said Leo, who is receiving therapy both physical and intellectual development, is now crawling, pushing buttons and is able to say "dad" and tries to say "mom."
"I love him [Leo] very much," she added. "One year ago, I couldn't imagine life with him and now, I can't really imagine my life without him. He's changed me so much. I can say I'm a different person now."