Kelly Osbourne: I'm in Charge of Dressing My Brother Jack's Baby!

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Jack Osbourne's fiancee Lisa Stelly is months away from giving birth, but his sister Kelly has already begun scouring baby boutiques for the latest designer fashions.

"I already told him that this baby, whether it's a boy or a girl, is going to be the best-dressed baby there is," Kelly 26, told Us Weekly at Macy's Material Girl Search in New York City Wednesday. "'You're not buying the clothes -- I am!'"

Kelly, who said she's "very, very excited" to become an aunt, certainly knows a thing or two about fashion: she was in the Big Apple to find the next Material Girl spokesmodel with Madonna's 15-year-old daughter, Lourdes Leon.

"This is not just a model position," Kelly explained. "You are a spokesperson and you have to do appearances, so you have to be a good public speaker and have confidence in who you are."

The E! Fashion Police critic added that their ideal spokesmodel must "love anything with fashion" and be a sartorial risk taker -- "just an all around true Material Girl."