Kim Kardashian: Niece Penelope Disick Is "Beautiful," "Absolutely Perfect!"

Kourtney Kardashian and Kim Kardashian arrive at the Elton John AIDS Foundation Academy Awards Viewing Party on February 26, 2012 in Beverly Hills, California. Credit: Jamie McCarthy/

Mazel tov, Auntie Kim!

Kourtney Kardashian gave birth to daughter Penelope Scotland Disick on Sunday, and her sister Kim was on hand (along with the rest of the famous reality clan) for the happy birth in Los Angeles.

"Welcome to the world, Penelope Scotland Disick! Kourtney gave birth to a beautiful baby daughter on Sunday and the whole family is so thrilled to finally meet her!" Kim, 31, wrote on her blog late Sunday.

Penelope, the second child for Kourtney, 33, and beau of five years Scott Disick, 29, who are already parents to 2-year-old son Mason.

Raved Kim of her brand-new niece: "She is absolutely perfect! I am so excited to be an aunt again and can’t wait to spoil little Penelope. I know Mason is going to be the best big brother in the whole world. Congratulations Kourtney and Scott. Xo

Us Weekly broke news of Kourtney's second pregnancy back in November.

"I'm really excited for Mason to not have to compete with a little brother!" Kourtney admitted on a recent episode of Keeping Up with the Kardashians.