What is the Difference Between Fraternal and Identical Twins?

Fraternal and identical twins have many differences. Identical twins are often described as those children resulting from a pregnancy that are identical to each other. Actually, more than resemblance is involved, and not all identical twins look “completely” alike, though they do share many of the same physical characteristics. As they age, they will have differences based on lifestyle choices, experiences, and a variety of other factors. Fraternal twins, though sharing a womb, have fewer commonalities, and both types of twins are most identified by how they begin life.

Most commonly, the way twins first begin life can be referred to as dizygotic and monozygotic. Dizygotic, or fraternal twins, result when a woman has two ova or eggs fertilized by two separate sperm. This can mean that fraternal twins are of different or the same gender. Though they are siblings, they do not share near identical genetic material.

Within each sperm or ova, there is variance in what gets inherited and expressed, and these children are as alike as siblings, which can be very alike or unlike. They also may share a special relationship because they shared a womb. Though these twins are the same age, however, they are usually easily distinguished from each other, just as it would be simple to tell apart siblings of different ages.

The conception of monozygotic (identical) twins is very different. Instead of two separate ova being fertilized by two sperm, these twins begin as one ova and one sperm. During the early process where the fertilized egg begins to produce more cells, it doubles itself and creates two embryos or two babies, instead of one. Since both babies are produced from the same fertilized egg, they share almost all the same chromosomes and DNA structure, and will bear remarkable resemblance to each other. They are truly more related than fraternal twins because of their beginning.

There are other differences between fraternal and identical twins. Identical twins are much more rare, and only 8% of all twins are identical. Moreover, fraternal twinning can be hereditary, but identical twinning is seldom hereditary and occurs with the same general likelihood in all populations.

There is much greater difference in the number of fraternal twins born in various populations, suggesting a degree of inheritance. Fraternal twinning is not always the product of genetics. Multiple births are less common in women who are vegetarians, and much more likely when women undergo fertility treatments to conceive.

Not matter how twins begin life, they will all have differences. Choices in life can make significant impact on which DNA gets expressed. This means identical twins will evolve along separate paths, though many of them stay very close. Most child development experts believe that both identical and fraternal twins should be encouraged to celebrate their individuality, since considering them as the same does not give each twin the opportunity to find his or her own gifts and strengths.