Khloé Kardashianis leaning on big sisterKim Kardashian Westfor mommy advice.

The realitystar and Good American designer, 34, tells PEOPLE exclusively for this week’s issue that mom of three Kim, 37, has been her go-to peer while learning the ropes in parenting her 3-month-old daughterTrue.

“I have to say that Kim probably has given the best advice because she’s not judgmental about any of it,” she explains. “She offers up different ideas and either you take it or leave it and that’s okay.”

Courtesy Calvin Klein

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TheKeeping Up with the Kardashiansstars posed alongside all four of her sisters — Kim,Kourtney Kardashian,Kylie JennerandKendall Jenner— for a Calvin Klein photo shoot while Khloé was eight months pregnant.

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“I think we were all a little more comfortable this time around, but shooting for Calvin Klein is always a little bit intimidating,” says Khloé (the sisters also joined forces fora #MyCalvins ad in Januarywhen Kylie, 20, was still pregnant with her now-6-month-old daughterStormi).

“Shooting in underwear eight months pregnant is even more intimidating!” Khloé admits to PEOPLE. “I stayed calm though, and it was nice tolaugh a lot with my sistersthroughout the whole day.”

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Khloé raves that it’s been “beautiful watching [her] family get bigger” with the addition of all the new babies, including Kim’s now-6-month-old daughterChicago.

“I have a lot to live up to watching my sisters do it,” she says of motherhood.

For more from Khloé Kardashian, pick up the latest issue ofPEOPLE, on newsstands Friday.

source: people.com