Kim Kardashian "Has No Idea" How Motherhood Will Change Her, Says Kourtney

Kanye West's pregnant girlfriend took out infertility worries on sister, later asked mommy advice

Kim Kardashian is in for some surprises when baby Kimye arrives.

At least, that's what big sis Kourtney thinks! Thursday on Ryan Seacrest's KIIS FM show, Kourt said Kanye West's pregnant girlfriend "has no idea" how much motherhood will change her life.

"I am so excited," Mason and Penelope's mom gushed. But, as you saw on Kourtney & Kim Take Miami, things weren't always amicable between the sisters when it came to having kids.

Before Kim, 32, knew she was pregnant, she quietly struggled with infertility issues and worried she might not be able to have children. "She was kind of taking it out on me," Kourtney, 33, recalled. "She was just criticizing me for being a mom…I think she was trying to psych herself out to make herself feel better. Like 'I don't want this life,' and 'Kourtney you're so boring…'"

Kourt said that "once [Kim] realized what she was doing, she was very apologetic." Only then did she reveal "what was going on."

But once Kim found out she'd been blessed with her and 'Ye's miracle baby, she turned to Kourt for advice. "She would just ask me all the time little things…Like, 'Can I have orange juice?'" Kourtney said. "And even though I just had been through it, it's hard to remember 'cause then you're kind of on to the next thing…I would try to say,' Oh you're not allowed to have hot dogs…nonpasteurized juices'...and just all the little stuff."

And Kourtney advised Kim not to commit to a set number of kids quite yet. She told Ryan, "You really don't know until you've lived with [having kids] and see if you want more, if you want less."

When it comes to Kimye babies, though, we're hoping for a houseful!