Quote:
Originally Posted by SaintessHeart
Blood sibling? Which person wouldn't be turned off by blood sibling? It is a psychological circuit-breaker that prevents the human race from wiping itself out via incest!
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The Westermark effect (the circuit-breaker) only kicks in if siblings (whether related by blood or not) have grown up together. There is even some suggestion for increased genetic attraction between closely related individuals if they are unaware of family ties and have never lived together.