Edi Stark finds out how the special bond between twins isn't always a happy one.

The difference in schooling between twins was the result of family choices, he notes.

We didn't speak often, since words aren't really necessary between twins.

That has not been necessary since the first kidney transplant between identical twins.

Researchers found the similarities between twins raised in separate homes with different parents to be remarkably strong.

They then examined just the wage differences between twins, while still controlling for education.

Other explanations have been given (and demonstrated) for different levels of development between twins.

On certain occasions a state of animosity can arise between identical twins.

This independent development contributes to the differences between identical twins.

For example, what would happen to sibling rivalries between twins born years apart?