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。

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 都会不舒服。

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

鸽子是成双成对地生活, 彼此非常恩爱。

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。