Christina Aguilera Sings 'Happy Birthday' to Fiance -- Plus See Her Adorable 2-Year-Old Daughter!

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They grow up so fast!
Christina Aguilera wished her fiance, Matthew Rutler, a happy 31st this week (his actual birthday is April 14), but in a new video shared to her guitarist guy's Instagram on Wednesday, it was the couple's 2-year-old daughter who looked to be getting a lot older!

In the sweet Instagram, Summer shyly helps Rutler blow out the candles, after Aguilera gives her man a nice birthday serenade.
The family of three is so adorable together, it almost hurts.
In February, Summer's mom and dad couldn't help but give their daughter the most adorable kiss attack.
Watch the video below for more.