Khloé Kardashian avoided pregnancy because of broken marriage

Reality TV star Kim Kardashian has stepped forward to explain why her sister Khloe Kardashian didn't have any children during her four-year marriage to Lamar Odom.

While appearing on Jimmy Kimmel Live Thursday, the 33-year-old designer revealed her sister avoided having children because she knew her marriage wasn't working.

"Khloe wasn't trying to get pregnant," Kim said. "She wasn't showing up to these doctor appointments on purpose and behind our backs because she knew [the marriage] wasn't working."

But even if she doesn't have kids of her own, Kim said her sister was "the baby babysitter" in the family.

Kim gave birth to her first daughter with fiancé Kanye West in July of 2013. The three of them are living at her mother Kris Jenner's house with her step sisters Kendal and Kylie Jenner.

On the subject of baby sitters, the new mom said her brother Rob Kardashian, "was the worst" one.

"I wanted him to spend time with [North] the last day and asked him to babysit for an hour," she recounted. "I pretended I had a meeting and he never showed up. Kourtney said it was the worse idea ever."

Asked about her mother's split from longtime husband Bruce Jenner, Kim said the separation was a long time coming.

"It wasn't a surprise," she admitted. "They have been living as friends for a long time. You want your parents to be happy. It was more awkward for them to live together and not sleep in the same room."

"I think it's the time away has gotten them back to that really good friend place and they realized they're better off as friends," she added.

Keeping Up With the Kardashians, a show that documents Kim and her family's life, premieres its ninth season Monday.

[Jimmy Kimmel Live]