Kim Kardashian is thrilled to be an auntie!

The curvy socialite is over-the-moon that her older sister Kourtney Kardashian gave birth to her first baby boy (with boyfriend Scott Disick) this week.

Writing on Twitter, Kim couldn’t wait to post about her newborn nephew.

She Tweeted: “I’m an auntie!!!!”

Which she then followed up by a second message that read: “My little Mason Dash Disick is here!!! We are so happy!”

Kourtney gave birth at Cedars Sinai in Los Angeles and he weighed 7 lbs. 6 oz, and measured 19.5 inches.

Kim recently revealed that she didn’t think her sister ever wanted kids, so she was super surprised to hear she was expecting.

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