Sarah Hyland Sends Sweet Birthday Wishes to Ariel Winter: You're 'The Little Sister I Always Wanted'

The 'Modern Family' star turned 19 on Saturday.

Happy birthday, Ariel Winter!

The Modern Family star turned 19 years old on Saturday, and her on-screen sister, Sarah Hyland, couldn't help but celebrate with a sweet pic.

WATCH: Ariel Winter Poses Topless in Unretouched Photos, Praises Sofia Vergara for Being 'Curvy Woman' Role Model

"Happy 19th Birthday to the little sister I always wanted but never had," Hyland wrote alongside a cute black-and-white shot of herself and Winter. "I know 19 is the most useless age as you get older but think of it as one year closer to your 20s! Love you so much @arielwinter ?."

WATCH: Ariel Winter Calls Out 'Fake Friends' on Twitter

While Hyland's post was simple and sweet, Winter herself got a little bit racy celebrating her friend Jessie Berg's birthday the day before.

"Happy birthday to my #1 wifey hoe??love you to the ?," Winter captioned a snap of the pair's backsides from a glass-lined pool.

WATCH: Ariel Winter Shows Off Curves in Sexy Form-Fitting Black Bustier

Berg returned the favor on Saturday with a black-and-white mirror selfie of the two and a message to her "wifey hoe."

"HAPPY BIRTHDAY lover!! can't wait to get married and grow old together!! :') forever my wifey hoe?," she wrote.

WATCH: Ariel Winter Rocks Plunging Dress on the Red Carpet With New Man Levi Meaden

Winter and Berg, along with a group of friends that included Winter's Modern Family brother, Nolan Gould, recently vacationed together in Bora Bora -- and didn't hold back when it came to posting sexy bikini pics.

See more in the video below.