LONDON, Jan 2 A mixed-race British couple has defied the odds — twice — by producing two sets of twins in which one sibling appears to be black and the other white.

The twins were born prematurely in November in Frimley, southern England, and spent several weeks in the hospital. They are now at home with their parents in Fleet, 60 kilometres southwest of London.

Dean Durrant's newborn daughter Miya has dark skin like him. Twin sister Leah has fair skin like her blue-eyed, red-haired mother, Alison Spooner.

Their older siblings Lauren and Hayleigh, born in 2001, also have strikingly different skin tones and eye colours.

“There's no easy way to explain it all. I'm still in shock myself,” Durrant, 33, told Sky News.

Both sets of twins are fraternal rather than identical, meaning they are the product of two separately fertilised eggs, so it is not unusual that they don't look alike. Miya's skin colour was more influenced by her father's genes, while Leah takes after her mother.

But scientists say it's rare for a couple to have two sets of twins, end even rarer for them to have such different appearances.

“Even non-identical twins aren't that common,” Dr Sarah Jarvis of Britain's Royal College of General Practitioners told Sky. “Non-identical twins from mixed parents, of different races, less common still. To have two eggs fertilised and come out different colours, less common still. So, to have it happen twice must be one in millions.”

The phenomenon is so uncommon that there are no statistics to illustrate its probability, although it is thought likely to become more common because of the growing number of mixed-race couples. —AP