Happy Birthday, Deacon Phillippe! Reese Witherspoon's older son just turned 12 — and we can hardly believe how grown-up he looks!

The 39-year-old star posted an adorable Instagram pic of mother and son together.

"Happy birthday to my sweet 12 year old boy! ???You bring joy to everyone you know. I feel so blessed to be your mom," the Oscar-winning actress wrote in the caption.

Reese and ex-hubby Ryan Phillippe also have a daughter, 16-year-old Ava Phillippe, who gave an adorable shout-out to her little brother with a super cute throw-back pic of the two as little kids.

RELATED: Reese Witherspoon Posts Heartfelt Message to Her Daughter Ava on Her 16th Birthday

Reese has a third child, three-year-old Tennessee, with husband Jim Toth and shared another photo of her two boys together. We can definitely see the resemblance!

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These two… ❤️❤️❤️ #BrotherlyLove

A post shared by Reese Witherspoon (@reesewitherspoon) on

The Legally Blonde and Walk the Line actress has frequently been spotted out with her whole beautiful brood in tow.

reese witherspoon and her three children

Reese Witherspoon with sons Deacon and Tennessee and daughter Ava

RELATED: Reese Witherspoon and Husband Jim Toth Fight Over Having Another Baby

Sending you birthday wishes, sweet Deacon! Hope the coming year is filled with all good things!