Kendall and Kylie Jenner Have a Secret Handshake and It Involves Boob Slapping

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Kendall and Kylie Jenner's unique, sisterly bond continues.

Kylie's Snapchats revealed the reality stars were working on their very own handshake this week, which apparently includes a grand finale where Kendall slaps her sisters boobs. Just watch:

WATCH: Kylie Jenner Sucks Kendall's Tongue Because Sisterhood Is a Deeply Personal Experience

Whatever is going on here, the two Keeping Up With the Kardashians sisters are apparently displaying that special bond that Kylie previously expressed by sucking Kendall's tongue. Another snap reveals the two dancing, and having a good time together.

In a post on Kendall's own page, the 20-year-old  model confirms that despite how in sync she and Kylie are, the moves were "unrehearsed."

WATCH: Kendall Jenner Gets Into Heated Altercation With Kylie

The new year has been all love for Kendall and Kylie.On New Year's Eve, Kendall posted a throwback photo of the two, with the caption, "I love you my sister."

Not that they always haven't been close. In late December, Kylie's "2015 recap" was, of course, a candid picture with Kendall.

And several days later, she posted another sister shot.

WATCH: Kendall Jenner Says Kylie and Tyga's PDA Is 'Annoying' During Family Vacation in St. Barts

Despite the love, the two do fight like sisters. A clip from KUWTK last year shows what happened at the ESPY Awards when Kylie wouldn't let her sister borrow a dress.

"You're just literally the biggest f**king bitch I've ever met," Kendall said during the heated exchange.

Watch Kendall talk about Kylie's priorities in the video below.