Travis Barker and Kourtney Kardashian no longer care about "hiding their relationship" as it's "gotten serious"

And he gushed that he "f******" loves the reality star.

The mother-of-three - who has Mason, 11, Penelope, eight, and Reign, six, with ex-partner Scott Disick - can be heard giggling in the clip: "Travis!"

He captioned the series of intimate pictures and video: "I F****** LOVE YOU!

"YOU’RE A BLESSING TO THIS WORLD.

"HAPPY BIRTHDAY @kourtneykardash (sic)"

And following the steamy post, it has been claimed that his girlfriend gave her 45-year-old beau "permission" to share the intimate images, as the couple don't feel the need to hold back on "showing PDA" when they are so loved-up.

A source close to Kourtney told Us Weekly: "Kourtney gave Travis permission to post the sexy photos of them.

"Their relationship has gotten more serious. Travis’ post on Instagram was just him wanting to let everyone in the world know how crazy he is about her."

They added that the Poosh founder also "doesn’t care anymore about hiding their relationship."

The source continued: "They love each other very much and their chemistry is off the charts. They’re always showing PDA."

Meanwhile, a source previously claimed that Kourtney is "really happy" with Travis.

The insider said of their romance: "He's always wanted to date her, but she would brush it off, and they continued to just have a friendship. Their relationship is going strong, and Travis has been treating her like a queen. He wants to do everything with her and is so excited about the relationship. It's going really well and Travis' kids love Kourtney. She's really happy and is having a lot of fun. They are planning a few more getaways together in the next coming months. Kourt is also helping Travis on his wellness line, and he loves hearing her input on the project."