News broke earlier this week that 21-year-old singer Justin Bieber and 36-year-old mom of three Kourtney Kardashian have been allegedly hooking up, and after the initial shock came mostly confusion, and Kourtney's little sister Kendall Jenner is just as confused as the rest of us.

"Kendall thinks the whole thing between Kourtney and Justin is weird. It's just creepy," a source told Hollywood Life. "First off, Justin is Kendall's good friend. He used to date her best friend Hailey [Baldwin]. Plus, he's just too young for Kourtney. He's a complete player and for the life of her, Kendall doesn't understand what Kourtney and Justin have in common. They both downplay their flirting with each other when they're around Kendall, but she's not an idiot. She knows something's brewing between them and it's just bizarre to her."

Bieber has even been bragging to his friends about hooking up with the oldest of the Kardashian sisters. "Oh yeah that's definitely happening and has been for some time now," a source told Us Weekly. "Every time Kourtney and Justin are together they're extremely flirtatious. They text each other all the time."

Now that the cat's out of the bag, even though we have yet to see any PDA from the two, they realize they need to be a little more private about their hooking up if they want to be able to continue on with it. "Now that people are on their trail they are going to move forward much more secretive," another source told Hollywood Life. "But they only plan to make the friends with benefits continues."

Neither Kardashian nor Bieber have yet to comment on the fling.