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An ageless grandma who is often mistaken for her son’s girlfriend has revealed she loves the awkward mix-up, because it helps keep her young.

Lisa Fox became a grandma last year at age 42 to her eldest son James’ child Archie and she’s absolutely loving it.

“When I found out I was becoming a grandmother I felt a lot of people around me thought I would see it in a negative way, a misconception that I would feel I was getting old,” she said.

“But it was the completely opposite, having a baby in the family is just such a joy, it in no way made me feel as if I was getting old.”

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Lisa had her son James when she was just 18, followed by daughter Hollie at 25, and her youngest, Jack, at 30.

But the mum-of-three is hard to tell apart from her 18-year-old daughter and says she’s often mistaken by strangers as her eldest son’s partner.

Lisa and Graeme Fox on their wedding day with her children, James, Hollie, and Jack. (Caters News Agency)

“I often get mistaken for James’ girlfriend and I even got a phone call from a friend who believed she had seen him walking down the road with another woman when it was in fact me,” she said.

The former estate agent added that being a young mum earned her extra street cred with her kids, being labelled a “cool mum” by their friends.

“I was always considered the cool mum and there has been a long-running joke with James’ friends that I’m a bit of a MILF,” she laughed.

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Lisa, from Newcastle Upon Tyne, said the fact her family was “very close” in age meant she had a lot of similar interests as the kids, including music, films and fashion.

And now that she’s a grandma, she can run around after her grandson much easier with husband Graeme, 43, than older grandparents.

“When I look back at my own grandparents, they wouldn’t have been able to look after young children, whereas I’m young enough to be able to run after them,” she said.

“So many people start younger now and it’s nice to see some more glamorous grannies around.”

This article originally appeared on news.com.au.