2 pair out on a Friday night, coupled. Yeah, a double date.

两对情侣在周五晚上出去玩玩，成双成对。是，四人约会。

Pigeons live in pairs, and the mates are very fond of each other.

鸽子是成双成对地生, 此非恩爱。

When your wife dies, it must be depressing to see other people in a loving relationship.

谁妻子死了 看见成双成对幸福 心里都会不舒服。

Not always, and not in pairs.

并不都是 更不会成双成对。

Only about 3% of mammals are monogamous, and, although 95% of birds pair off (at least for one breeding season) , paternity tests have revealed that the avian world is chock-full of cheaters.

只有大约 3% 哺乳动物是一夫一妻制，虽然 95% 鸟类都是成双成对（至少在一个繁殖季节内），但亲子鉴定显示，鸟类世界充满了骗子。