Kim Kardashian, Kanye West invited momager Kris Jenner and her new boy toy Corey Gamble to celebrate KK's 34th birthday in Las Vegas at Tao -- the May-December couple even joined Kimye on their private jet.

So just WHO is this guy Corey that the 58 year-old grandmother is dating? It's Justin Bieber's co-manager -- who works with Scooter Braun and he's reportedly in his early 40s.

Kris had a lot to keep up with, as daughter Kim busted out in a white dress with plunging neckline for her birthday bash at Tao. Khloe kept it simple in a little black dress with black workboots (yikes!) and Kanye wore a patterned sports coat in black-and-white.

So back to Kris' boy ... he supposedly told OK! magazine he met Kris at Ricardo Tisci's birthday bash: "I approached her and found out we actually lived pretty close to each other." The pair were snapped at a Calabasas restaurant out on a date last week. Gamble told the mag, "That worries me and I'm hoping it's not a setup from Kris because I do really like her."

Looks like this romance is heating up!