The This Morning presenting pair have both paid tribute to their son's milestone birthday on Instagram.
Ruth's only child and Eamonn's fourth looks like he enjoyed a high-end birthday breakfast celebration.
The television star shared a video on Instagram of a glam dinner table set out with silverware, giant '18' balloons and plenty of glitter.
And an extra special birthday breakfast seems a bit of a tradition in their household, as hinted in her the video's caption.
Ruth, 59, shared with her some 765,000 followers: "The scene is set! Traditional birthday breakfast table for Jack’s 18th!!! Our baby’s all grown up!!"
The caption was followed by a baby emoji, and many of her fans couldn't help but leave a glowing comment.
One user commented: "Amazing table! Happy 18th!" and another posted: "Happy 18th birthday Jack have a beautiful day. The years go so fast I remember when he was born and you took him on Loose Women enjoy your day."
Meanwhile Eamonn, 60, shared a rare photo of their son Jack, who is rarely seen in the spotlight.
Sharing a beaming father son photo to his some 588,000 followers, Eamonn gushed over how proud he was of his youngest child.
He wrote: "My Baby Son becomes 18 today , all grown up and at least 6 inches taller than his old Dad.
"Couldn't be more proud of the young man he has become. Many Happy Returns Jack."
One of his fans couldn't help but point out that the pair share a remarkably similar nose.
The user wrote: "Same nose," with smiling face and nose emojis.
Eamonn must have seen the likeness himself and replied: "Haha... you're right Bridget!"
Another user complimented the pair with: "Eamonn Holmes he certainly has your good looks."
And a further user posted: "Happy birthday Jack. What a lucky young man to have two wonderful parents."
Eamonn has three further children with his first wife, Gabrielle Holmes - Declan, 31, Rebecca, 29, and Niall, 27.
He spoke candidly about his marriage breakdown in an interview with The Guardian in 2013.
He said: "For me, the failure was not to hold together the husband and wife bit, the failure in the heart came from not being able to hold together a family life.
"I think we will always be pleased that we'll always have a bond between us – all of us."
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