There have been some rumors that Kendall and Kylie are experiencing a bit of sibling rivalry lately, so when Kylie didn't join the fam in wishing Kendall a happy b-day on social media AND was absent for her birthday lunch, it seemed to add more fuel to that fire.
"It is a competition between them now as to who can be the more famous Jenner and it is destroying their relationship," a source told RadarOnline. "It's sad. They used to be so close and now they are really letting this fame thing affect them!"
We did a little digging of our own and yes, Kylie was a no-show for Kendall's birthday lunch, but so was her dad Bruce Jenner, so was Kim Kardashian and so was Rob Kardashian. They were probably just busy.
Only Khloe, Kourtney and Kris joined the birthday girl at the Hotel Bel Air, so something tells us that wasn't Kendall's official birthday party. They'll probably all do something this weekend.
For what it's worth Kendall and Kylie are also promoting their new PacSun holiday collection together AND Kylie just posted this pic of them three weeks ago. Note the caption.
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Gallery | Kendall and Kylie Jenner: Stylish Sisters