Christina Aguilera, Matthew Rutler

Kevin Mazur/Getty Images for The Apollo

They grow up so fast!

Christina Aguilera took to Instagram on Sunday to wish her and fiancé Matthew Rutler's baby girl Summer Rain a happy first birthday.

The adorable pic shows their little girl in a cute pink outfit. "Happy 1st birthday! My sweet, Summer Rain," the 34-year-old singer captioned the sweet B-day snapshot. How gorgeous are Summer's bright blue eyes?!

Rutler also tweeted a daddy-daughter photo with the message, "You light up life. Happy First Birthday, Summer." Too darn cute.

Christina Aguilera Instagram

Instagram

Aguilera gave birth to little Summer back on Aug. 16, 2014.

Shortly after her arrival, a source revealed to E! News the story behind Summer Rain's name. "Christina wanted something different and unique for the baby's name," the insider said. "She loves how Summer Rain Rutler flows together and thinks summer is an amazing time of the year. She has always been a more expressive person and a little bohemian who is inspired by words and daily life."

In addition to celebrating Summer's first birthday, Aguilera and Rutler also did a little partying in the Hamptons over the weekend. Aguilera even hung out with Real Housewives of New York star Bethenny Frankel. Frankel shared a cute pic of them enjoying cocktails on Sunday.

Aguilera and Rutler also attended the Apollo in the Hamptons event on Saturday.

Christina Aguilera Instagram

Instagram

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