B&W twins - One in a million

Kylie Hodgson gave birth to twin daughters by caesarean section, then she realised a difference between them.

This amazing conception happened after two eggs were fertilised at the same time in the womb.

The odds against of a mixed race couple having twins of dramatically different colour are a million to one.

Skin colour is believed to be determined by up to seven different genes working together. For a mixed-race couple, the odds of either of these scenarios is around 100 to one. But both scenarios can occur at the same time if the woman conceives non-identical twins, another 100 to one chance.

This involves two eggs being fertilised by two sperm at the same time, which also has odds of around 100 to one.

If a sperm containing all-white genes fuses with a similar egg and a sperm coding for purely black skin fuses with a similar egg, two babies of dramatically different colours will be born.

The odds of this happening are 100 x 100 x 100 - a million to one.