Kendall & Kylie Jenner on Kanye West: "He's Amazing. Kim Is So Happy"

At the Teen Choice Awards, the two young stars sound off on their sister's rapper BF

Kendall and Kylie Jenner are talking sister Kim Kardashian's boyfriend Kanye West. And yes, they approve!

"He is very sweet. We've known him for a long time," Kylie, 14, just told me on the pink carpet at the Teen Choice Awards. "Kim and him have been friends forever. He's been nothing but nice."

Kendall, 16, gushed, "He's amazing. Kim is so happy."

Do they think there's a wedding in their future?

"I don't know," Kendall said with a laugh. "If that makes Kim happy."

The two said they couldn't talk too much about their new baby niece, Penelope, but Kendall cooed, "She's beautiful."

Penelope's big brother Mason is adjusting quite nicely to having a sister. "He's the best," Kylie said.

PHOTOS: Keeping Up With Kimye