VIDEO : Christina Aguilera Wishes Baby Daughter Summer Rain a Happy First Birthday

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. the 34-year-old singer captioned the sweet B-day snapshot."Happy 1st birthday! My sweet, Summer Rain." Rutler also tweeted a daddy-daughter photo with the message, "You light up life. Happy First Birthday, Summer." Aguilera gave birth to little Summer back on Aug. 16, 2014.