Horse owners Gayle Lawrie and Lee Fairbairn were shocked after their 14-year-old thoroughbred mare, Tarn, gave birth to healthy twin foals.
Twin foals rarely survive birth, and if they do, are often born weak and die soon after.
Now five days old, Rio and Holly are strong, healthy and have a good chance of survival.
"They were on wobbly legs for a couple of hours," Ms Lawrie said.
"But now Holly is running around. She has kicked me twice. And Rio is very cuddly and goes to sleep in my lap."
Veterinarian Neil Twentyman said the likelihood of twin foals surviving was less than 1%.
"I have been a vet for 24 years and this is the first instance of safe twins I have been involved in."
He said Tarn's large abdomen had allowed the twins to survive. The size of two foals usually would stretch a horse's uterus, resulting in premature birth.
Normal practice was to scan a pregnant horse and abort one of a twins to allow a foal to survive.
Luckily, Ms Lawrie did not have Tarn scanned, and did not expect twins.
Equine reproduction expert Dr Lee Morris said successfully giving birth to twin foals was extremely rare.
"Ninety percent of cases of twins - we eliminate one of them," she said.
"The mare is different from the cow. Foals have really long legs and twins compete in the uterus for nutrition."
Dr Morris said twin foals were not to be encouraged because, in many cases, both the foals and the mare die.
"It's definitely an undesirable event. Sometimes if they do survive, they are retarded in development or one is bigger than the other. It's amazing that you've got healthy foals in this case though - she's very, very lucky."
Ms Lawrie, a self-confessed "animal freak" and long-time horse owner, said she had seen many dead twin foals, but no lucky survivors.
She was woken at 5.15am on Christmas morning by a foal alarm, a device which monitors when a horse has lain down to give birth and alerts the owner.
After the arrival of the first foal 10 minutes later, Ms Lawrie was concerned when she found a large protruding bag coming out behind his birth sack.
She was shocked when another head emerged, with a shiny black eye looking at her.
"It was a miraculous end to a crappy year," said Ms Lawrie.
"I have lost a piece of property, lost a cat to cancer, a puppy to illness, and my Shetland foal broke its back and my leg."
