This theory is the basis of a famous thought experiment known as the twin paradox, in which a twin sibling who travels on a fast-moving rocket ship would return home younger than the other twin.

这个理论基础来自于著名试验猜想，双胞胎悖论：乘坐高速火箭飞船旅行的双胞胎哥哥（或弟弟），回到家后要比他的弟弟（或哥哥）年轻。

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There, you may see a brother, a sister, a step-sibling, a twin.

那里你可能看到兄弟，或者姐妹，或者异父母同胞，或者双胞胎兄妹。

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But if one twin has bipolar disorder, the other twin is more likely to develop the illness than is another sibling.6.

但是如果双生子之一有双相情感障碍，那么另一个比起其他兄弟姐妹更可能患病。

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Dr. Pedersen, a professor in the department of medical epidemiology and biostatistics at Karolinska Institute, currently studies dementia among twins, including the recent research showing that an identical sibling of a twin with dementia has an increased risk of also developing the condition.

WSJ: Twins Health Registry Is Treasure Trove for Medical Research