The 37-year-old Oscar-winning singer said it was a digital romance for him and his future wife, as they tried to keep in touch in the early days of their relationship while they were apart.
The couple started dating after they met on the set of Legend's music video for his hit Stereo in 2007. They got engaged in December, 2011, and married in Lake Como, Italy, in 2013.
"I fell in love with her over the phone because she is good with those 140 characters," he joked to Entertainment Tonight about his romance with the Sports Illustrated model.
"(At the beginning of our relationship) we were texting a lot, and I started to see her sense of humour," he explained. "We would talk on the phone, and I started to fall in love with how engaging and witty and funny she is."
"And I think that's when I really started to know that this was the kind of person I wanted to be around a lot," Legend shared. "Once we started spending more time together between tour stops and all this other stuff, we realised we had such a connection - and then it blossomed into a marriage and a baby."
Legend famously penned his romantic ballad All Of Me to his wife, and the pair welcomed baby daughter Luna in April this year (16).
He said he wasn't nervous by the instant connection the pair had when they first started dating, but he knew then that Teigen could be 'The One'.
"I wasn't nervous about it," Legend confessed. "When you feel a real connection to somebody, for me it wasn't nerves, it was more like excitement. 'Oh, this could be great.'"
The singer is currently promoting his new movie, Southside With You, which is based on Barack and Michelle Obama's first date.
"The movie is such a great love story and makes you feel their romance, and it makes you believe in the power of love and of people finding the person that is really the right match for them," he said.
The award-winning musician even wrote a song for the movie, and said, "The song (I wrote) is called 'Start,' and the idea behind the song is we don't know unless we start, so we have to try it. We have to engage. I felt like that was the message Barack was trying to give to Michelle in the film."
Despite the Obamas not yet seeing the finished film, Legend has no doubt that they'll love the romantic drama, which he co-produced. "I told them about it the last time I saw them and encouraged them to see it, and we will make sure they get a copy if they haven’t seen it yet," he said. "I think they will like it."
Southside With You is to be released in the U.S. on 26 August (16).
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