Gigi Hadid and Bella Hadid don sexy ensembles for Bella's 21st birthday

Happy birthday Bella Hadid!

The model turned 21 on Monday, and she celebrated her milestone birthday in typically stunning fashion as she rocked revealing ensembles and surrounded herself with family and friends.

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On Monday night, Bella stepped out with sister Gigi, 22, and as they left her birthday dinner holding hands, they made jaws absolutely drop. Bella rocked a sexy satin LBD with lace-up sides and leather studded straps. She finished her look with strappy black heels and a high pony.

See their looks for Bella's 21st birthday in the gallery below:

For her part, Gigi was a total vision in an all-baby-blue ensemble that put her fit physique on display. The model rocked high-waisted slacks with a super sheer, strapless corset top and, at one point in the night, she threw a matching blazer over her shoulders. She paired the look with matching satin heels and a simple updo.

Mother Yolanda Hadid, 53, went for a most restrained look, rocking a chic all-black outfit that she pulled off with aplomb.

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Earlier in the day, Bella turned even more heads when she shared a video on her Instagram Story that quickly showed herself rocking a simple t-shirt and a barely-there thong. The video was taken of a still photo on a DSLR camera, and it's unclear exactly when the initial photo was taken -- but it was still incredibly sexy nonetheless.

The racy snap isn't out of the ordinary for the new 21-year-old, who has never been shy about showing skin or flaunting her model physique.

See the revealing picture she posted -- and more of her sexiest Instagram moments from 2017 -- in the gallery below:

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