Kourtney Kardashian and Travis Barker’s relationship didn’t happen over night. The longtime friends took their time before they decided to explore a romance, HollywoodLife has learned. And, it was the drummer who made the first move.

Travis Barker was the one to initiate a relationship beyond friends with Kourtney Kardashian. “He just finally made a move and that’s how things went to the next level. He couldn’t hide it anymore,” a source close to both the Poosh founder, 41, and Blink 182 drummer, 45, told HollywoodLife, exclusively, noting that Kourtney felt the same.

“She’s had a thing for him too, but wanted to respect everyone’s boundaries, like with their exes,” Scott Disick and Shanna Moakler, the source said. Though, the couple’s  transition from being friends to something more wasn’t hard for their kids. “They all know each other and are aware of what’s going on between them. Plus, Kourtney and Travis hung out as friends for years, is it’s nothing new for the kids and they’re all fine with it,” the insider explained.

Kourtney shares three kids with her ex: sons Mason, 11, and Reign, 6, and daughter Penelope, 8. Meanwhile, Travis has a son, Landon, 17 and daughter Alabama, 15, from his previous marriage to Moakler.

While Kourtney and Travis are “exclusive” as a couple and “very happy,” their relationship “is still nothing too serious at this point,” the source said. “There’s a lot of passion and chemistry between them, but they’re just exploring taking things from a friendship to a romantic relationship right now. Travis is very sweet and romantic towards Kourtney, and so far, it’s been easy,” the insider explained, adding, “Things are definitely continuing to blossom.”

Kourtney and Travis were close friends for years before they went public with their romance, via Instagram on February 16. At the time, they shared identical hand-holding photos, which showed off Kourt’s Valentine’s Day manicure and the rocker’s tattooed hand. More recently, Kourtney visited Travis at work, where she snapped two stunning photos of herself in a dimly lit studio. Rumblings of a romance between the two began in January when they enjoyed a weekend together at Kris Jenner’s home in Palm Springs.