They have both lived in Dallas "so they have that Texas thing in common," a source close to the singers tells PEOPLE. "They're both very spiritual and mature for their ages. They are in a committed relationship."
Colton and his band, who have previously opened for John Mayer, Maroon 5 and Dave Matthews Band, are currently on a break from the tour, recording a follow-up to their 2004 debut CD Drive, in Los Angeles. But the couple plan to reunite Dec. 7 in Hidalgo, Texas, as they close the tour out with a nine-city jaunt that ends in San Jose two weeks later.
While Colton won't be joining Clarkson when her three-week UK/Ireland tour kicks off in Manchester in February, it seems the pair will find plenty of quality time off the road.
"It's very serious," says the source. "He's just a great guy and very normal. They're totally into each other."
And in other Idol news, the fifth edition of the show – to begin Jan. 17 – will remain on Tuesday and Wednesday nights, despite strong rumors that FOX was going to switch it over to Wednesdays and Thursdays. "You don't mess with a good thing," network entertainment president Peter Liguori tells The New York Times.