Mandarin

Mandarin ducks. According to Wikipedia,

In the eyes of ancient Chinese, they form a life-time couple, unlike many other species of ducks.
...Therefore, they became the symbol of conjugal affection and fidelity. :)))

Also, if you place them in your room, this will help you find your soulmate, or keep them if you've already met them.

AND you also have to believe. :)