To mark the milestone birthday, Gordon shared a series of photos of his lookalike son, which melted the hearts of his many followers. The first photo captured how much of a loving father the Hell's Kitchen star is with Oscar sat firmly on his shoulders, and the pair sporting the biggest grins on their face.
Another snap saw Gordon taking a selfie while carrying his smiling boy in one arm, while a third photo saw Oscar sat on a yellow jeep and a fourth saw him pretending to be the Michelin Man as he stood behind the iconic mascot.
In a touching caption, the 56-year-old penned: "Happy 4th Birthday to my wee man @oscarjramsay love you so much best mate Dad."
Oscar's other family members, including mum Tana and sister Tilly, also shared tributes to the youngster with a selection of sweet images.
Fans loved the adorable photos, as one commented: "It's been 4 years already? Wow," while a second said: "Happy Birthday to your handsome lil wee man! Enjoy!"
A third commented: "Happy birthday Oscar they grow up so fast. I hope you're having a great day. Gordon!" and a fourth added: "He's your mini-me."
Gordon's followers have recently been surprised with how fast young Oscar is growing up, and last week they were delighted as he posed alongside older sister, Holly.
In an image posted to the youngster's Instagram account, which his family runs, Oscar could be seen grinning in a mirror as Holly took a selfie with her arm around her youngest brother.
Perhaps replicating how he pronounces his sister's name, the caption read: "Hobby came to play!!" Commenters shared their appreciation, with one writing: "So grown up," and others agreeing: "Getting tall Oscar," and: "Can't believe how he has grown…"
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