Now, each egg and each sperm was generated by the process of meiosis, which begins with genetic recombination in the process called "crossing over." So each egg and each sperm have slightly different genetic information. This is why fraternal twins look slightly different from one another!

Can fraternal twins look completely different?

Fraternal twins don't share identical DNA and are no more genetically similar than any other siblings. They can be opposite sexes and can look completely different from each other.

Why do fraternal twins not look alike?

Since fraternal twins are the result of different eggs and different sperm, they share the same percentage of chromosomes as any other siblings. The National Human Genome Research Institute says that this is about 50 percent. This is why they don't look exactly alike and can be assigned different sexes at birth.