Your Twins: Identical or Fraternal?


Often the parents of young twins want to know whether their twins are identical or fraternal (non-identical). Identical twins are born from the same fertilised egg, or zygote, whereas fraternal twins are born from different eggs. Twins who are of opposite sex are always fraternal.

Identical twins usually look very much alike. Sometimes people mix them up and call them the wrong name. Fraternal twins can be as alike, or unalike, as brothers or sisters. It is often easy to tell them apart, even when they are little.

There is a questionnaire which can help parents decide whether they think that their twins are identical or fraternal. It is called a zygosity questionnaire. It asks how much the twins physically resemble each other, and whether people get them mixed up. It is designed for parents to use when their twins are young, and seems to work quite well for most twins. One scientific study asked parents to complete the questionnaire for twins aged between 18 months and 4 years old.

If you would like to complete the questionnaire, please click on the link below.

Complete Questionnaire

Last updated 2 July 2001 by Tom Price