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Sophia Grace and Rosie are all grown up! See the cousins celebrate Rosie's 15th birthday

The cousins rose to fame when they appeared on "The Ellen DeGeneres Show" in 2011.
Sophia Grace And Rosie Visit Westfield Southland In Melbourne
Cousins Sophia Grace Brownlee and Rosie McClelland celebrated an important milestone together this week.Andrew Batsch / Newspix via Getty Images
/ Source: TODAY

Where did the time go?

Rosie McClelland turned 15 years old this week and it's hard to believe that she's all grown up!

The teen became a YouTube sensation in 2011 after she appeared on "The Ellen DeGeneres Show" with her cousin Sophia Grace Brownlee and performed the world's cutest cover of Nicki Minaj's "Super Bass."

On Wednesday, McClelland shared a photo of herself with Brownlee, now 18, and thanked her cousin for helping make her birthday so special.

"Love you @therealsophiagrace thank your for my amazing present and spending my birthday with me!!!! 💖" she wrote.

The adorable little girls, who became regulars on DeGeneres' talk show, have grown up into young ladies in front of our eyes and the birthday girl seemed equally in awe of how quickly time has passed.

"15 & 18 how did that happen? Together since I was born, traveled the world together, never had a single argument and still by each others side! Big things to come and I can’t wait for you all to see!!!!" she captioned the post.

Brownlee replied to her pal's post, writing "Love youuuu ❤️❤️❤️."

McClelland also shared a series of other photos from her birthday festivities, including one of a pretty impressive balloon display.

She also teased her fans with a vague update and suggested that she has some fun projects planned for the coming year.

"So excited for the next year, music, tv oh and did I mention I just got a ********* can’t say but will tell you all soon 🤩🎥 🎤 ❤️," she wrote.

In April, Brownlee turned 18 and McClelland made sure to wish her pal a happy birthday on Instagram.

"Happy 18th Birthday for yesterday! " she wrote. "Forgot to post these. Had the best day celebrating with you and love you so much."