Are twins God's mistakes?

Was just wondering about this the other day. You know how people keep telling you that you are unique just like everyone else? That there is something about you that is specific to only you, that sets you apart from the rest? That God has made you this way that there is something about you that defines you.

What happens to twins then? Are they God's mistakes? If every one of us is one of a kind, what wrong did the twins do? Of course I am attributing uniqueness to appearance, but well, it is a well-known fact that twins often tend to have similar liking and disliking for stuff. In such a scenario, are twins then forfeited the right to be unique just because they were born together? And if that is true, then why do we consider twins special?

Or is it that being twins is the something that sets them apart from the rest? But what about each other? In fact, come to think of it, does the whole 'uniqueness' concept even matter? Or rather, is it even important? If man is a social animal, and he spends more than half his life trying to blend in, then why on earth would he want to seem different?

Are we generally different people who co-exist out of need? Or are we generally similar people who co-exist in spite of our differences?