Selena Gomez and her rarely-seen little sister Gracie wore matching outfits to 'Frozen 2' premiere

She's the Anna to her Elsa.

Selena Gomez unexpectedly brought her younger sister to the Thursday night premiere of Disney's "Frozen 2," marking the first major public appearance ever made by 6-year-old Gracie Teefey. The sisters walked the red carpet in perfectly-matching outfits: Bell-sleeved bohemian maxi dresses topped with feathered floor-length capes.

The two shared a quick peck in front of the cameras, and Selena couldn't stop smiling as they entered the premiere together.

"Hope I’m officially the best big sissy ever now," Selena captioned a photo of the twosome. "She was LIVING her best life!! 'Frozen 2' was amazing!"

The siblings may have a 21-year age difference between them, but that has no bearing on their sweet bond: "They were so cute," an insider told Us Weekly. "Selena was talking to her sister closely before the movie started, and she was smiling and giggling."

Gracie is one of Selena's two half-siblings, one on her mother's side and the other on her father's. Her other sister, Victoria Gomez, is five years old.

The "Frozen 2" premiere proved to be a family night out for a number of famous faces! Sterling K. Brown brought the whole adorable clan (and all dressed in blue!): He and his wife, Ryan Michelle Bathe, were joined by their two sons, Andrew and Amare. Meanwhile, Ashlee Simpson and husband Evan Ross walked the red carpet with daughter Jagger Snow Ross and Bronx Wentz, whose dad is Fall Out Boy frontman Pete Wentz.

See all the red carpet arrivals in the gallery below.