A kitten born with two faces and a large, merged middle eye is thriving despite concerns its health would deteriorate after birth.

Bettie Bee was born in Eastern Cape, South Africa on December 12, along with two other cats.

The owner had difficulty nursing the kitten and became concerned the newborn would starve, according to Newsweek.

Instead they brought Bettie Bee to a cat rescuer, who now cares for the cat and posts updates and photos for thousands of people following its progress.

The rescuer said on Facebook the kitten was "doing well" and "growing nicely".

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She is a diprospus or Janus cat. The name "Janus cat" was coined by British zoologist Dr Karl Shuker, based on the two-faced Roman god of transitions, gates and doorways.

Domestic cats with two faces are extremely rare and typically die young, but Bettie Bee is showing promising signs — eating and gaining weight at a healthy rate.

A photo of Bettie Bee on scales showed after 10 days she weighed 200 grams, a healthy weight for a kitten at that stage of growth.

The kitten can be fed by either mouth as both lead to the stomach, the rescuer told Newsweek.

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Frank and Louie lived to 15

Frank and Louie, a famous feline who held the Guinness World Record title for the longest lived Janus cat, lived until 15.

"The normal life expectancy is one to four days for cats with this condition," because afflicted animals typically have other disorders and defects, Frank and Louie's owner said.

"When he was first born, every day was a blessing."

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At a day old, the kitten was brought into a veterinary medicine university to be euthanised. Marty, an employee at the university, offered to try and save the cat.

Marty, from Massachusetts in the United States, immediately adopted Frank and Louie and helped him get surgical procedures necessary for survival, she said.

He went onto become the longest surviving Janus feline, entering the record books at 12 years old. Frank and Louie died in 2014 at age 15.

The cat had one brain, so both faces acted in unison. Two of his eyes — the outermost ones — were normal, while the middle eye was larger but did not function.

Marty said in 2011 Frank and Louie was "actually more like a dog. He walks on a leash and he loves car rides".

ABC/wires