Celebrity chef Gordon Ramsay, who has five children, has opened up about his bizarre identity crisis as a parent.

Ramsay has Megan, 22, twins Jack and Holly, 20, Matilda, 19, and Oscar, 19 months, with wife Tana, and he says people think his youngest child belongs to his older son and he is the grandfather, when they all go out together.

"The worst thing is when I'm walking with Tana and Jack, and everyone is looking at Jack as if Oscar is his son... 'You must be so proud to be a grandad'," Britain's Men's Health magazine, reports femalefirst.co.uk.

The 54-year-old celebrity chef is also a fitness enthusiast and is happy that his children have followed in his footsteps when it comes to endurance events.

"My son Jack did his first Ironman 70.3 last year. I got all the kids entrance into the London Marathon, raising money for Great Ormond Street Children's Hospital. Tana is going to commit to her 10th marathon. I've got my 15th London coming up, two LAs and five ultras. It's starting to rub off on them," said Ramsay, adding that he finds cycling uncomfortable.