Humans are not the only species that can express faithfulness, many other animals can offer examples of how to keep a relationship together. Even though lifelong pair bonds are fairly rare in the animal kingdom, there are a few animals that can keep it together.
Gibbons will form an extremely strong bond with their mate and spend time grooming each other and hanging out together
Swans can form strong pair bonds that can last for many years or even for life. Swans have become a symbol of love because of their loyalty and while swimming together their necks form a heart.
French Angelfish are rarely alone, they form monogamous bonds that often last a lifetime. They will live, travel and hunt in pairs.
It's no wonder that Turtle Doves come in pairs in the classic "The Twelve Days of Christmas".
Source: Mother Nature Network