Their romance sounds like it was plucked straight from a country song.
But Star magazine is now revealing that the 26-year-old schoolteacher was married when they started dating.
And, according to court documents, her now ex-husband said he wanted a divorce on the grounds of "adultery."
The revelations are a far cry from the romantic tale Gilbert, 29, told the media about the hometown girl who re-won his heart.
"I'm a blessed man to have her back in my life, and I can't wait to make her my wife," the "You Don't Know Her Like I Do" singer recently said.
He also gushed, "She was the one that got away for about five years. It came back around, and I've never been happier."
Gilbert and Cochran first met 10 years ago near his hometown of Jefferson, Ga.
But, after they split, she went on to marry Brock Anderson, whom she met at college.
They got married in November 2012. But, according to a source, in late 2013 Cochran started spending more time with her family in north Georgia.
In January this year all seemed well with the Andersons but in the spring, the insider says the schoolteacher reportedly "disappeared one night when she said she was going to the grocery store – then never came back..."
In March she filed for divorce and her husband countersued on the grounds of adultery.
The pal says, "I remember when Brantley announced in October that he was engaged to a then-unnamed schoolteacher.
"We all thought how wild it would be if it turned out to be Amber – and Brock said, 'I'm pretty sure it is her'."
To read the full story, pick up the latest copy of Star magazine.