Snapchat / Kylie Jenner / . 1 / 6
Snapchat / Kylie Jenner / . 1 / 6

Some might say Kylie Jenner has a big mouth.

The 18-year-old reality star took to Snapchat on March 28 (using a filter which plumped up her lips even more) while hanging out with sister Kourtney Kardashian, who also sported the same big lip treatment, and the mother-of-three's estranged boyfriend Scott Disick.

In the snap, Kylie started teasing her sis after Scott had claimed in an earlier Snapchat that he and Kourt were back together.

"So I heard on Snapchat you were back together," Kylie said, addressing Kourtney and Scott, who were all together in a makeup room.

"Did you not hear me say 'no' at the end," Kourtney shot back, referring to the earlier video of her and Scott on her Snapchat account.

Then a persistent Scott chimed in, "She's just playing hard to get. She's just kidding."

Earlier that day Kourtney recorded herself and Scott and then shared it to her Snapchat story.

While looking into the camera, Scott said earnestly, "We wanted you guys to hear it first... we are back together."

Kourtney quickly set the record straight, however, interrupting and saying, "No," emphatically before the video cut off.

Of course, Kylie - who last year admitted to having lip injections - quickly seized on the opportunity to get in on the joke, and then set about asking Kourtney and Scott all about their "reconciliation" via her Snapchat account, complete with the big-lip filter for extra comedy value.

Kourtney and Scott split last July, but remain on good terms and spend a good deal of time together. They have three children together; Mason, aged six, Penelope, aged three, and 15-month-old Reign.

She recently clarified their relationship status on Snapchat, saying, "By the way, everyone relax. We have three kids together. We spend time together."

While Scott clearly still has a soft spot for Kourtney, he's now moved on with 20-year-old model Christine Burke.

Meanwhile Kourtney was at the center of rumors in December that she had a fling with 22-year-old Justin Bieber.