Reese Witherspoon and Ryan Phillippe Reunite for Son Deacon's 18th Birthday

Reese Witherspoon and her ex-husband, Ryan Phillippe, reunited for a special occasion over the weekend, celebrating son Deacon's 18th birthday together as a family. Phillippe shared sweet photos from the family outing to Instagram Sunday, as the proud parents pose with the birthday boy, who is seated in front of an impressive cake.

"Happy 18th birthday to our gorgeous, smart, talented, and caring son," Phillippe wrote in the caption. "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." The Wish Upon actor added in an aside to his ex, "I'd say we did pretty good @reesewitherspoon." Deacon responded to his dad's emotional post, "Thanks dad!! I love you," with Witherspoon adding, "So proud of our boy ... I mean our ADULT Son!"

The Morning Show actress penned her own birthday note to her son, writing alongside photos from throughout Deacon's life, "How did this happen?!! @deaconphillippe is 18?!! 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." The birthday boy responded, "Love you mom!!" Witherspoon and Phillippe are also parents to 22-year-old daughter Ava and have been working to co-parent since splitting in 2006 after seven years of marriage.

In August, Phillippe went on a bonding trip with Deacon to the McCauley Warm Springs in New Mexico, writing alongside photos from their trip, "The rocky uphill hike was well worth the warm woodland baptism that followed." Deacon chimed in, "And the viddles." Another of these father-son trips was of a more extraterrestrial theme, as the actor shared on Live with Kelly and Ryan in November that he and his son had just gotten back from Joshua Tree National Park, where they were hunting for aliens.

"We did some rock climbing and this and that. I had rented an alien-themed Airbnb and then revealed to him that the actual intent of our trip was to try to make contact with alien civilization," Phillippe said, adding that while they had "a great father-and-son bonding moment," there was "no alien contact."