"Kourtney and Travis are in total lust over each other and she doesn’t regret going public with their relationship at all," the source says.
"The relationship was a long time coming because the attraction has always been there on both sides," the source adds. "They love the fact that they have a true friendship and bonded that way before taking anything further and making things romantic."
ET learned in January that Kardashian and Barker had started dating after years of being friends. During an appearance on The Drew Barrymore Show last week, Barker said the pair's relationship "comes natural," especially since they're both parents.
Kardashian is mom to 11-year-old son Mason, 8-year-old daughter Penelope and 6-year-old son Reign, whom she shares with ex Scott Disick. Barker is dad to 17-year-old son Landon and 15-year-old daughter Alabama, whom he shares with ex-wife Shanna Moakler.
"I would date girls that didn't have kids and I find it kind of hard, because I think they have trouble understanding, well, 'Why don't you want to go to dinner every night with me?' or 'Why don't you want to see me every night?'" Barker told Barrymore. "Now, I'm spending time with a woman who's, like, a great mom, who's, like, a great friend and you don't have to worry about any of those things, it just comes natural."
"I also really like missing someone and cherishing the time that I spend with them, instead of, you know, every day being with them, especially in the beginning of the relationship," he added. "I think missing someone is so important."
Barker also honored Kardashian in a post for International Women's Day on Monday.