Kim Kardashian Is 'So Excited' For Pregnant Sister Kourtney

Reality-TV star says new 'Kourtney & Khloé' show captures her family's reaction to the news.

If Kourtney Kardashian, who is expecting her first baby in December, thought younger sister Kim would be jealous of her impending motherhood, she'd better think again. Kim says she couldn't be happier for her.

"I will be an auntie!" Kim exclaimed to E! News. And though Kourtney herself said she was shocked to discover she was pregnant, Kim said she wasn't surprised by the news. "No, it's my sister, so not at all. ... I'm so excited for them!"

Kim also shared that the whole Kardashian clan has known about the baby "from the moment it happened. You will have to tune in to see how it really happened and how it all went down on Khloé and Kourtney's show," she said. "We capture the entire crazy experience."

On Thursday, Kourtney called into Ryan Seacrest's radio show and said she hadn't been expecting to be a mom anytime soon and had figured that Kim would be the first to start a family. "She definitely thought it was going to be her first. Kim has, like, every baby name picked out," Kourtney said. "I don't think she was envious, but who knows? Kim gets mad if I get, like, the car that she wants. She, like, freaks out."

The star of "Kourtney & Khloé Take Miami," which premieres this Sunday on E!, said she found out she was pregnant while filming the show. "Out of all of us, I was definitely the last one that was even thinking about [having children]."