Fraternal twins are siblings who were born at the same time but grew from two separate eggs. Unlike identical twins, who look nearly the same because they came from one egg that split in two, fraternal twins can look as different from each other as any other siblings. They might have different hair colors, different heights, or completely different facial features. Fraternal twins can even be different sexes: one boy and one girl.

Think of it this way: regular siblings are born years apart from separate eggs. Fraternal twins are also born from separate eggs, but they happened to grow in their mother's womb at the same time and were born on the same day. They shared the experience of being born together, but genetically they're no more alike than any other brothers and sisters.

Fraternal twins can be two brothers, two sisters, or a brother and sister. About two-thirds of all twins are fraternal rather than identical. Because they grew separately, fraternal twins can have different personalities: one might be quiet and thoughtful while the other is outgoing and energetic.