Marna Schacknies has 15-month-old boy/girl twins, and she's learning that there's a lot of confusion out there about male and female twin pairs. "Most people don't know the difference between identical and fraternal twins," says Schacknies of Berkeley Heights, N.J. "We are usually asked, 'Are they both boys?' despite the fact that my daughter is always wearing something girly and usually pink. And right after we tell people, 'They are a boy and a girl,' they will inevitably ask, 'Are they identical?'"

If you're expecting a set of opposite-sex twins, you're probably already bracing yourself for questions from the general public – and you may have some questions yourself! Here is advice on what to expect and how to prepare.

Boy/girl sets are always dizygotic, or fraternal, twins. Dizygotic twinning occurs when two separate ova (eggs) are fertilized by two different sperm. Dizygotic twins aren't always male and female. In fact, there is equal chance of them being two boys or two girls.

No matter how similar your little ones may appear, they are not identical. The term "identical" refers only to monozygotic twinning. This occurs when one ova is fertilized by one sperm and then divides into two afterwards.

From a genetic standpoint, boy/girl twins aren't different than any two full siblings who were born at different times. However, a powerful bond often exists between these little ones.

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