What better time to cut loose than at your big sister's wedding?
In fact, the longtime friends were actually seen "making out" during the lavish reception following the ceremony at the Forte di Belvedere in Florence, Italy, a source tells E! News.
Well, there was a lot of romance in the air! What with John Legend singing "All of Me"—live—for Kanye West and Kim's first dance as husband and wife, the flowers, the food, the fun in the photo booth...
Who wouldn't want to celebrate with a kiss?!
Will Smith's son was also seen heading for the airport with Kylie and the rest of the Kardashian-Jenner crew this morning.
And yes, everyone looked as if they had just woken up after having the time of their lives last night.
Kylie, like all of her sisters (including the bride, of course), wore white dresses to the party. Khloe Kardashian's curve-hugging dress made for a sexy rear view in an Instagram pic she shared today as she bid Florence farewell as the family caught a flight back to Paris.
New episodes of Keeping Up With the Kardashians premiere June 8 at 9 p.m. on E!