Selena Gomez Becomes a First-Time Big Sister ― at 20!

Selena Gomez now has a little sister to share clothes with … but it's just going to be a long time until they wear the same size!

The 20-year-old singer-actress has become a big sister for the first time as her mother, Mandy Cornett, and stepfather, Brian Teefey, welcomed their first child together in Los Angeles this week. The baby's name and other details have not yet been announced.

Gomez pal Demi Lovato was one of the many celebrating when the news broke Thursday night.

"@SelenaGomez IS A BIG SISTER!!!!" the "X Factor" judge tweeted. "Everyone congratulate her and her family!!!!!" That was followed by another post, simply: "#CONGRATSSELENAMANDYANDBRIAN," which became a trending topic.

And congrats are especially in order because Cornett, who married Teefey in 2006, publicly suffered a miscarriage in December 2011. Gomez, who had shared the baby news with her fans two months earlier, quickly canceled her public appearances and withdrew from the spotlight to spend time with her family.

In May, Gomez revealed her mother's pregnancy by posting a sweet photo, taken on Mother's Day, on Twitter. In the pic, the "Spring Breakers" star is standing next to Cornett with her hand lovingly on mom's belly.

"Hope all the amazing moms had a great day," Gomez wrote. "I have the best momma in the world :)) I love you so much!"

While Gomez has long waited for a sibling, she certainly comes armed with experience. When she was dating Justin Bieber, she often spent time with his younger half-siblings. In fact, Gomez sweetly brought young Jazmyn, 5, and Jaxon, 3, as her dates to the "Hotel Transylvania" premiere last year — though it wasn't without toddler drama.

“They loved it," Gomez told Entertainment Weekly of the experience. "We lost some shoes, and they got really excited, but it was good."

Aww! Well, we can't wait to see dote on her own little sis, who will one day get the mother lode of amazing haute couture hand-me-downs.

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