Kim Kardashian West "felt bad" for Kendall Jenner when Tyga joined their family vacation.

Kendall and Kylie Jenner with Kim Kardashian West

Kendall and Kylie Jenner with Kim Kardashian West

The 20-year-old model slammed her younger sister Kylie Jenner for bringing her rapper boyfriend on the girls' trip to St. Barths and her older half-sibling can understand her frustration.

Kim told E! News: "When Kylie showed up, because she came like a day later, Kendall was so excited for them to spend time together and Kylie brought her boyfriend, she just didn't know about it.

"Kendall had all this stuff planned and then it was like, 'Oh there goes my girls trip.' She was just so excited to spend quality time with Kylie and just had she been prepared it would've been a different story. I felt bad for Kendall, kinda."

However, Kim - who recently gave birth to her and husband Kanye West's second child, son Saint - insists relations between the two sisters aren't "rocky".

Speaking after the vacation drama aired in the first of a two-part 'Keeping Up With the Kardashians' special last night (20.12.15), she said: "It's not rocky. We just thought it was a girls vacation."

During the episode, Kendall admitted she didn't feel "very important" to Kylie when Tyga was around.

She said: "I was really looking forward to being with Kylie on this trip.

"Not that I don't love Tyga, but having him around kind of takes Kylie away from me. I don't think spending time with me is very important to her."