We were shocked when we saw Justin Bieber and Kendall Jenner's super-flirty Instagram pics, but apparently those kissy photos are also causing major drama in the Jenner household. According to Heat magazine, Kylie is furiously heartbroken that Kendall has been spending time with Justin, her crush.

"Kendall knows full well that her sister loves Justin. Kylie's been desperate to date him for a long time, so for Kendall to hook up with him is pretty poor form," their source said.

"LA is nine hours behind Spain, so it was the middle of the afternoon when Kylie saw Kendall's steamy Instagram pictures with Justin. She tried to pretend that she didn't care, but she was close to tears. It's caused a major split in the family, with everyone taking sides."

Justin wished Kylie happy birthday on Instagram by saying that it was "so dope" watching her grow up, which definitely makes it seem like he sees her as a little sis. If Kylie is holding a flame for Justin, that would be so heartbreaking for her. We hope Kendall and Kylie aren't fighting — they're so close!

Still, we don't know if we believe this report. Kylie is rumored to be dating Justin's close friend Jaden Smith, and when Kylie and Justin started hanging out earlier this summer, there wasn't much romance there. Plus, the Jenner sisters did attend the Teen Choice Awards together, along with their older sis Kim Kardashian, and we didn't notice any major tension.

Do you think Justin would cause such a big rift in Kendall and Kylie's relationship? Are Kendall and Justin really dating? Let us know what you think in the comments!