Michael and Amanda Biggs with twins Marcia, bottom, and Millie, top

Both come from families with a history of twins. Their own set were born by Caesarean section at Good Hope Hospital in Sutton Coldfield. Amanda said: "We never knew how different they were going to look. Their different appearance settled down after a few months, but it means that Millie now looks like her dad, with black hair and dark skin, and Marcia takes after me.

"But they're also now developing their own different personality. Marcia's the more laid-back, chilled one, and Millie's the crafty one."

Jane Denton, director of the Multiple Births Foundation, said: "This is an unusual case but it is difficult to say how rare. Nobody records the skin colour of every twin in the UK. It wouldn't be politically correct to do such a thing.

"We have 10,000 twins a year in the UK and we can expect this to happen in certain situations.

"What has happened is that two separate eggs were fertilised by two separate sperm.

"The genes that go into defining skin colour will be different which results in a combination of genes."

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