Kylie Jenner -- Inside Her 18th Birthday Blowout ... Mom & Dad's Odd Moment (PHOTOS)

Kylie Jenner's 18th birthday party almost got really, REALLY awkward when her parents ended up in the same booth ... with Kris Jenner's boyfriend!

We got these pics from inside Sunday night's bash at Bootsy Bellows -- and you can see Kylie, her sisters and their significant others all having a great time. But poor Corey Gamble ... at one point in the evening he became the meat in a Kris-Caitlyn Jenner sandwich.