Bear Grylls fans could not get over his son’s height after he shared a snap of the teen towering over him.

The TV adventurer originally shared the photo of him and Marmaduke earlier this year, to mark his middle son’s 18th birthday. But it has a new lease of life this week after an image of Gary Barlow with his own tall son went viral.

Posted on Instagram, Bear’s shot showed him and his wife Shara smiling with Marmaduke, who looked as if he were dressed for graduation. “18 today! We love you so much Marmaduke… keep shining bright!” he wrote.

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But fans were just distracted by how much taller Marmaduke was than his famous dad. Bear is apparently around 5ft 10, and it’s thought his son is well over 6ft.

“He’s a big lad!” one fan remarked in the comments section, as another person quipped: “What are you feeding him?!” “You must look up to him a lot,” joked somebody else.

Another exclaimed: “Size of the kid!” “He’s huge sir,” said someone else, as another impressed fan noted that the teenager looked as if he were “incredibly strong”. “OMG.. those are some good genes,” posted one person.

Other people joked that Marmaduke was the “real bear”. “Look at the bloody size of him! A bear of a man,” said one. “Bear cub is getting stronger,” said another.

Other fans urged the TV star to encourage his son into sports, saying he was likely to be brilliant. “Get him on that rugby pitch,” said one, as somebody else wrote: “Now if he isn’t a rugby player, he should be!”

Bear, 50, and his wife Shara tied the knot in 2000 and they have three sons together. Marmaduke is their middle son and they also have Jesse, 21, and Huckleberry, who is 15.

Earlier this week fans were stunned to see a picture of Take That star Gary’s son Daniel. The image shared online showed the singer with Daniel, 24, who was several inches taller than his pop star dad, completely dwarfing him in the sweet family shot.

Gary, 53, and wife Dawn also have two daughters – Emily, 22, and Daisy, 15.