Reese Witherspoon Celebrates Son Deacon Philippe's 18th Birthday With Ex Ryan Phillippe

Deacon Phillippe's birthday was a family affair!

Reese Witherspoon, 45, took to Instagram and shared several pictures of her son taken through the years on Saturday in honor of his 18th birthday.

"How did this happen?!! @deaconphillippe is 18?!!" she captioned the post.

"One day he was trading Pokémon cards, singing Bruno Mars songs, and playing American Ninja Warrior in the backyard. The next day, he is taller than me, cooking the family steaks on the grill and making his own music with his best friends," she continued.

"My heart is bursting with pride about the young man he is becoming. Happy 18th Birthday Deacon! I love you to the moon around the sun and all the stars ✨ 🥺❤️🎂" she added.

Deacon was touched by the beautiful tribute and commented, "Love you mom!!"

Fans and several well-known personalities sent birthday greetings Deacon.

"Geez--Xtra Handsome bugger ! Nobody in my high school or college looked like that--yikes!! 😄" noted actress Jennifer Coolidge.

"Wow! I can’t believe it!! Happy birthday ❤️" a follower wrote.

"18 wow, HBD young man 😍" another one commented.

Reese posted more snaps on her Instagram Stories featuring the birthday celebrant, including a lovely family picture with her ex-husband, Ryan Phillippe, 47.

The "Cruel Intentions" co-stars got together for their son's big day.

Ryan uploaded two family pics on his account, along with a touching tribute.

"Happy 18th birthday to our gorgeous, smart, talented, and caring son," he wrote. "You are a true light in this world and are so loved by all who know you. We are lucky to be your mom and dad."

He added with a shoutout to his ex-wife, "Love you, pup..(I’d say we did pretty good @reesewitherspoon)," to which the "Legally Blonde" actress replied by saying, "So proud of our boy ... I mean our ADULT Son! 😮❤️"

Ryan's followers reacted to the post, including Deacon who wrote, "Thanks dad!! I love you."

Some fans praised him and Reese for their co-parenting.

"What a testament to the love & support you’ve both provided. Beautiful family inside & out," noted a supporter.

"oh my goodness 😢😢😢😢😢😢 I’m not crying!!! Best co-parenting couple ever and always one of THR most iconic couples EVER❤️❤️❤️😢😢😢😢👏👏👏👏 congratulations 🎉," quipped another.

Ryan and Reese were married from 1999 to 2008 and share two children together -- Deacon and Ava Phillippe, 22. In 2011, Reese married Talent agent Jim Toth, and together, they share son Tennessee James, 9.

During Interview's Summer 2021 cover story, Reese got candid about watching her kids grow up.

"That makes me want to cry, the idea of having a long relationship with adult children," she told Tracee Ellis Ross in June.

Reese continued, "I never expected the kind of relationship that I have with them, but it's so rewarding to be able to have kids that you can process life with a little bit, and they help me understand the complexities of what it means to be a human now. So I'm really, really grateful that these little humans are in my life."

She added, "Adult humans. I have two adult children now, Tracee. It's crazy."