Non-identical twins are the result of two fertilized eggs implanting in the uterus at the same time.

非同卵双生胎是两个受精卵同时在子宫着床的结果。

《柯林斯英汉双解大词典》

Velia: no, they're non-identical twins. A girl and a boy. The boy was born first.

维莉娅﹕不是，是不相同的孪生婴儿，一女一男，男的较先出世。

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Before then, both identical and non-identical twins have largely independent odds of reaching a given age.

那之前，无论同卵还是异卵双胞胎在达到某一既定年龄时都在极大程度上有各自不同的几率。

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And it is only a predisposition towards having non-identical twins that is passed down through families.

BBC: Royal baby: What are the odds of twins?

Another American scientist, Robert Plomin, has been working with 25, 000 pairs of identical and non-identical twins in Sweden.

ECONOMIST: WHAT WE LEARN FROM TWINS: The mirror of your soul | The

Mr Plomin has also set up a study working with 10, 000 pairs of identical and non-identical twins in Britain.

ECONOMIST: WHAT WE LEARN FROM TWINS