On Monday Kendall Jenner's 19th birthday festivities continued into the wee hours of the night, and while she was joined by Cara DeLevingne and a number of pals, she got pretty chummy with older sister Khloe's ex-boyfriend French Montana. That's even more inappropriate than her 17-year-old sister Kylie dating 24-year-old rapper Tyga!

While Kylie and Kim skipped out on Kendall's birthday luncheon in Beverly Hills on Monday, both of them attended the bash last night, and Kendall posted a series of Polaroids on Instagram while French posted the above shot of himself with the birthday babe. Though Khloe and French seem to be on slightly better terms these days, it does strike us as a bit odd. And speaking of odd, what do you make of Kim's bleached eyebrows?

Kim tweeted the pic below and wrote, "About last night... #KendallsBDayParty #DontBeScaredOfMyBleachedBrows #ItsForAPhotoShoot ... #EyebrowsOnFleek" ... we're curious to see more!