Tori Spelling and Dean McDermott mark their son’s milestone birthday in sweet posts.

The former couple took to their Instagram account on Friday to celebrate their son Liam’s 18th birthday.

“It’s official my 1st born is an adult…” Spelling began as she shared a series of pictures of Liam.

“They say don’t blink because they grow but no one prepares you for how fast it goes. 18 years ago today my beautiful Liam Aaron McDermott aka Monkey made me a mama.”

Spelling went on to share that Liam was an easy child, and it gave her a sense of purpose in life.

“It’s a hefty weight being the oldest of five. A lot of responsibility that you’ve proven over and over to take on gallantly,” Spelling penned. “The way you’ve stepped in to protect me emotionally shows how love has no boundaries.”

“You will always be my baby. While I cannot physically hold you in my lap anymore, with arms wrapped around you know that my heart is forever wrapped around you,. I cannot wait to see where this journey leads you.”

On the other hand, McDermott, also penned a sweet note for Liam along with a series of snaps of the father-son duo.

“This little man is no longer little. My baby boy Liam is 18 years old today!! I can’t believe it,” McDermott said in his caption. “He’s such an awesome dude and I’m so proud of him. Happy 18th Liam. I love you so much!!#keepflyingyourfreakflag.”

It is pertinent to mention that McDermott and Spelling share five kids together, Beau, 8, Finn, 12, Hattie, 13, Stella, 16, and Liam.