What is the difference between identical and fraternal twins?

twinsIdentical twins (also called monozygotic twins) occur when one fertilized egg splits and develops into two (or occasionally more) fetuses. The fetuses usually share one placenta. Identical twins have the same genes, so they generally look alike and are the same sex. A woman’s chances of having identical twins are not related to age, race or family history.

Fraternal twins (also called dizygotic twins) develop when two separate eggs are fertilized by two different sperm. Each twin usually has its own placenta. Fraternal twins (like other siblings) share about 50 percent of their genes, so they can be different sexes. They generally do not look any more alike than brothers or sisters born from different pregnancies. Fraternal twins are more common than identical twins.

Triplets and other higher-order multiples can result from three or more eggs being fertilized, one egg splitting twice (or more), or a combination of both. A set of higher-order multiples may contain all fraternal siblings or a combination of identical and fraternal siblings.  Read our fact sheet if you want to know more about being pregnant with multiples.

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15 Responses to “What is the difference between identical and fraternal twins?”

  1. Bella Says:

    I am a Identical twin, my daughters are idential and their daughters are identicla Hows that.

  2. Lindsay Says:

    Bella -Wow, that’s rare! Thanks for letting us know!

  3. Precious Palesa Latlhang Says:

    My cousins are identical twins and as they were growing up they would get the exact same answers even though they sat far apart from each other in their class such that they had to be separated as they continued with their studies…………

  4. Tameka Williams Says:

    My cousins are fraternal twins and they look like identical twins! So cute

  5. Beth sarver Says:

    My brother and I are faternal twins but were born at separate times although we are identical with different birthdays we are considered faternal.

  6. Jane Jensen Says:

    I have twin sisters who do not look alike at all. Very different in character, also. They were born in 1941 about 20 minutes apart. I guess they are fraternal twins.

  7. Adrian Rodriguez Says:

    Hi my name is Adrian and my sis and i are fraternal twins but don’t act or loom the same

  8. Ametorwu Richmond Says:

    My self and my brother are fraternal twins but we were born at different time and we do not look alike

  9. Monica Says:

    I’m having identical triplets crazy all three are in the same sac will they be the same

  10. Alyson Says:

    My younger sisters are fraternal twins. They are the same sex, but they do not look alike. Though, they tend to have the same behavior in some things, but other stuff, they are complete opposites

  11. Zytreea Says:

    These websites are bananas i have a identical twin sister and fraternal twin brothers this only go off science not real life my mom has no sisters and brothers and my great uncles on my mom side are twins. On my dad side my great grandmother has twins on her side identical.

  12. Sara Says:

    Hi Zytreea. Wow–you have a lot of twins in your family! If some women in a family have had fraternal twins, it is more likely that others will have twins, too. You’re also more likely to have multiples if you’ve been pregnant before, especially if you’ve been pregnant with multiples. But you are right, not every family who has twins, has a history of twins. Thanks for sharing your family’s story!

  13. Steve Love Says:

    Hi how much wind and my brother and I are totally opposite in everything we don’t look like we don’t act like we deafly don’t do things like no I’ll characteristics of mannerism are the same women think differently

  14. Steve Love Says:

    Correction my brother and I are totally opposite in everything we do we don’t look alike we don’t think alike or characteristics and mannerism are totally opposite even Ourwait & our bodies And how we look at things and deal with things they say opposites attract what happened to us

  15. gracyn Says:

    most everything is right but the information given about the identical twins says that identical twins can be the same gender but actually it is always the same gender because the egg splits and two offspring’s are genetically identical meaning the gender is also genetically identical. see what I mean, but other than this there is mostly no misconception on the article.