The reason for this is because fraternal twins are formed when two different egg cells are fertilized by 2 different sperm cells.
Identical twins are caused by the splitting of a single fertilized egg.
Fraternal twins are no more similar than a brother and sister, but identical twins share the exact same DNA.
Fun Fact: I take Psychology and I learned that a test was done to see the personality differences between the two. Fraternal twins act just like two siblings (because they are indeed from two different eggs), while identical twins act and think nearly the same, if exposed to the same influences as well.
