Strangers will have a hard time telling them apart. And, although they may look and act alike, they are two separate, distinct human beings and should be treated as such. At birth, your doctor can usually determine whether you have fraternal or identical twins, but not always. You will know for sure after a few months. They will either continue to look identical, or they'll develop important physical differences in appearance.
Twins are twice as much work, but also twice as much fun.
The Parenting Resource Center on the Web.