Posting a series of photos from a celebratory 18th birthday dinner on the weekend, Ryan wrote a sweet message to his son.
"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. Love you, pup. (I’d say we did pretty good Reese)."
Commenting with a love heart emoji, Reese wrote that she was "so proud" of their son before sharing Ryan's post on her Instagram Stories.
Sharing her own carousel of images, Reese got sentimental on Instagram on Deacon's special day, with stars like Gwyneth Paltrow, Mindy Kaling and Octavia Spencer leaving their well wishes.
"How did this happen?!! Deacon is 18?!! One day he was trading Pokémon cards, singing Bruno Mars songs, and playing American Ninja Warrior in the backyard," Reese wrote.
"The next day, he is taller than me, cooking the family steaks on the grill and making his own music with his best friends. 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."
His big sister Ava also shared an Instagram shoutout, welcoming Deacon into 'adulthood.'
"I cannot believe the first baby I ever held is now 18 years old. D, you’re simply the best. Funny, loyal, intelligent, genuine, kind, passionate, creative… and the list goes on.
"You light up rooms and always look for the best in people. Watching you grow into who you’re meant to be is such a joy, and I’m eternally grateful to be your big sister."
Reese and Ryan famously acted together and were married from 1999 to 2008. It's fair to say fans were shocked to see the duo looking almost exactly the same as they did back in their Cruel Intentions days.
"I thought this was a throwback picture and the dude was a co-star from 2001. You and Reese do not age," one fan wrote on Ryan's post, with another adding: "You all look like you just turned 18."
Ava and Deacon are often featured on their parent's social media pages, with many fans commenting on how much they look like their famous parents. While Ava shares a few more similarities to her dad, Deacon is almost an exact mini-me of his mum.
"I really don't know who looks more like who," one fan wrote in the comments.
"The Witherspoon genetics are strong AF! Such a pretty family," said another.
Fans were also happy to see the divorced duo together on the occasion, with many commending them for their co-parenting efforts. We certainly love to see it!
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