Tres Johnson has craniofacial duplication and doctors told his parents Brandy and Joshua that their son was unlikely to survive at almost every stage of his life, The Sun reports.

The youngster, from Missouri, USA, was born with a large cleft, two separate nostrils, an abnormally shaped head, cognitive delays and suffers seizures.

There are only 36 people in the world with the condition — caused by what’s known as the Sonic the Hedgehog (SHH) gene which alters the formation of the skull.

Tres has amazed doctors, who didn’t expect him to live and four years ago said there was nothing more they could do after reaching his teens.

He has undergone multiple operations to reshape his skull and close his cleft, as well as treat his seizures, which have reduced from 400 to 40-a-day since starting cannabis oil treatment, his parents explained.

Tres Johnson has turned 13. Picture: Brandy Johnson/Caters News

Tres received more than 14 different diagnoses before doctors realised he had craniofacial duplication, also known as Diprosopus — the Greek word for “two faces”.

Brandy, 35, who is also his fulltime carer, said: “He was adorable and shocking at the same time, one side of his face looked like our older son, the other resembled our middle son.

“When he was born he had such a large cleft that it went up into his nasal passage and you could see into his sinus cavity as it was all open.

“His one eye looked like it was bulging out and the other sucked in, because his eyes are further apart he sees peripherally instead.”

Doctors doubted whether he would survive and mum-of-three Brandy says the first glimpses of her son were difficult.

“When they bought him into my room he was hooked up to a carrier box with all of his monitors, the only thing I could touch was his leg,” she said.

“Doctors weren’t going to sustain Tres and planned to let him pass if my husband hadn’t fought for him.

“Once I found out he was here and still alive that was all that mattered to us