A mum says strangers are left gobsmacked when they see her baby boy - who already wears clothes meant for three-year-olds.
Alexa Priego, 31, gave birth to baby Kason 11 months ago - but his size often fools people.
Her youngest son was born at a normal weight of 7lb 14oz but, after two months of breastfeeding, he became huge - and has just kept growing since.
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Watch a video clip of mum Alex and baby Kason below:
Alexa, a hospital administrator, said: "He is the heaviest baby in the whole world.
"He's very tall and very chunky - doctors said he is in the 99th percentile for weight and height.
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"When people see him they ask his age, and they are shocked when I say 11 months because they expect him to be older.
"People are so amazed by it - but when my daughter was born, she was exactly the same.
"I guess I just make big babies!"
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Alexa, also mum to Owen, 10, and Gracie, four, said doctors explained that she overproduces milk which could contribute to Kason's huge size.
Despite his size, Kason is an otherwise healthy baby.
Alexa says: "He is the easiest baby to look after - he's so easy-going and always smiles at people.
"He crawls and can walk when he holds onto the side of the couch and tries to stand on everything.
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"He is a very active boy. He crawls really fast too - he's very speedy for a big boy!"
The mum-of-three adds that people just can't get their heads around Kason's age and size.
People even stop her in the street to question his age - and their jaws drop when they learn he isn't even one yet.
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She said: "They expect him to be much older. Their reactions amaze me sometimes - I'm like, 'is he really that big?!' I guess I just make big babies!"
Isobel Pankhurst