In December 2012, Dongsar, 30, happened to be watching a YouTube video called High School Virgin when he saw a young woman who looked just like his good friend, Bordier, 27, a fellow fashion design student in London.
"I kept clicking onto the next link and then, for some strange reason, I started watching this video," he tells PEOPLE. "There was this girl that looked very familiar. I thought, 'That looks a bit like Anais.'
"But then I was like, 'It's not possible because this girl is American and Anais is French.' So I sort of let it be."
A couple minutes later, he was more than shocked when he saw the woman in the video turn around and smile. "I thought, 'That is the same smile Anais has as well!' That just blew my mind. It was actually like seeing Anais in the video."
He immediately took a screen shot of the young woman in the video and posted it on Bordier's Facebook page, joking, "When were you going to tell me that you were an actress?"
The shocking post caused an uproar among their mutual friends. "Everyone was like, 'Tell us where you got the video. This is bizarre.' Anais was in shock as well," he says.
Bordier and Dongsar tried to find the woman's name but couldn't since the YouTube video had no credits.
The Amazing Story of Identical Twins Separated at Birth Who Find Each Other 25 Years Later
Fate stepped in again weeks later when Dongsar happened upon yet another video featuring the young woman – this time in a promo for the 2013 movie, 21 and Over. Unlike the YouTube video, the movie credits revealed the young woman's name: Samantha Futerman.
"I couldn’t believe I found her again," says Dongsar, who has his own company, Kelsang Dongsar – a London-based creative and luxury fashion brand consultancy with clients including Kewa and Paul's Boutique.
"I was like, 'This is definitely strange. Something real is going to happen here.' "
Armed finally with a name, Bordier went to IMDb and was stunned when she saw that Futerman, a Los Angeles-based actress who had appeared in the 2005 movie, Memoirs of a Geisha, was born in South Korea, like her – and was born on the same day, November 19, 1987. Like Bordier, she had also been adopted – Bordier to a couple in Paris and Futerman to a New Jersey family with three boys.
When Bordier told Dongsar that she and Futerman shared the same birthday and were born in the same place, "We were just gobsmacked," he says. "That entire day was just a blur. It was almost like we were in a movie and being set up because it was so bizarre."
Adds Bordier: "I was in a state of pure shock."
After talking about how to approach Futerman, Bordier decided to message her on Facebook.
Futerman did indeed check it. "The first thing Sam did before she even said hi was that she sent her documents with her birthday and birthplace to Anais straight up. It was insane.
"I mean, it was quite possible that this could be Anais long lost twin," he says. "You build up hope and there is the possibility of disappointment that she is not. But she was."
The twins met for the first time in London on May 14, 2013. While seeing each other in person for the first time "was awkward, like a first date," says Futerman, their discomfort quickly dissolved, with the two bonding instantly – even taking a nap together that first day.
Last year, the sisters, who confirmed with a DNA test that they are indeed twins, wrote a book about their incredible journey, Separated @ Birth: A True Love Story of Twin Sisters Reunited.
They have also shot an award-winning documentary called Twinsters, chronicling the moment they met, how they have forged a relationship over two continents – and the close bond they share as twins.
Says Anais, who grew up as an only child: "Finding Samantha changed my life. I cannot imagine what my life would be like without Sam. It's wonderful to have an extended family now."
So does Dongsar. "I am really close with Sam now," he says. "It's just like being with Anais, only she speaks [with an American accent]. Her friends have become friends of ours as well. It's such a happy story. It all just feels right."
For more on Anais and Samantha, pick up this week's issue of PEOPLE, on newsstands Friday.