I'm not sure this could be done, but I think it would be nifty:)

Some twins love being twins, others do not. If it were possible I think it would be cool to randomly have twins that either like being twins or dislike being twins. If they like it, they do everything together. If one gets pregnant, and the other does not, the other sits with her until the baby is weaned, or the mother twin follows around the unladen twin while she works. If the twins do not like being twins, they refuse to work together. If one is harvesting the crops, the other will walk away.
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Why is it that if someone tells you that there are 1 billion stars in the universe you will believe them,
but if they tell you a wall has wet paint you will have to touch it to be sure?