"Travis has been in the Kardashians' inner circle for many years now, and he's always had a soft spot for Kourtney — and vice versa," an insider tells OK!.
"It never felt right for them to date or hook up until now, mainly because they were scared it might mess up their friendship," the insider continues. "But the chemistry has always been there. And finally, they've decided to give this a go, have as much fun as possible and see where it takes them."
According to the insider, the reality star, 41, and the Blink-182 drummer, 45 — who've lived in the same neighborhood for years — quietly took things to the next level about three months ago.
"The overwhelming view is that Kourt deserves to have fun and explore her feelings for this guy, who has an exciting edge to him," shares the insider.
"They usually hang out at each other's houses, but also enjoy walks on the beach and hikes, as well as dinner and movie nights," the insider says, adding that their kids sometimes tag along too. (Kardashian is mom to Mason, 11, Penelope, 8, and Reign, 6. Barker has Landon, 17, and Alabama, 15.)
"They've taken them go-karting and done some other outdoor activities like water sports and soccer," adds the insider. "Kourtney's been having a great time with Travis — and everyone in her inner circle is really excited for her."
Including her kids' father, Scott Disick, 37. "He's cautiously pleased to see her happy," says the insider, noting that he's "keeping a close eye on the situation," as any protective father would do.
But at the end of the day, adds the insider, "Scott's in no position to be prying on Kourtney's life or trying to preach about who she gets to date."