Khloé Kardashian is leaning on big sister Kim Kardashian West for mommy advice.

By Jen Juneau and Brittany Talarico
Kardashian Sisters 1
Credit: Courtesy Calvin Klein

The reality star 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 daughter True.

“You get so much advice when you’re becoming a new mom,” says Khloé, who welcomed baby True with boyfriend Tristan Thompson on April 12.

“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.”

The Keeping Up with the Kardashians stars posed alongside all four of her sisters — Kim, Kourtney KardashianKylie Jenner and Kendall Jenner — for a Calvin Klein photo shoot while Khloé was eight months pregnant.

“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 for a #MyCalvins ad in January when Kylie, 20, was still pregnant with her now-6-month-old daughter Stormi).

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

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 daughter Chicago.

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