虽然是双胞胎，但这两兄弟的性格却截然不同。

[误] Though the two brothers are twins, their dispositions are quite different.

[正] Though the two brothers are twins, their dispositons are as like as chalk and cheese.

注：虽然是“不同”，但却不用 different，而是用 alike(相同的)。chalk 和 cheese 形似而实不同，这看似矛盾的措辞用在这里倒能产生令人难忘的效果。