It's that time of year again, and as you snuggle up to your loved one, you may wonder how natural it is to only have one partner. For humans, it's tough to say if monogamous behavior is more socialization or biology.

In the animal kingdom, however, biology rules. Only 3 percent of species are monogamous, and even within that tiny minority, there are cheaters.

Sorry to burst your love bubble, but even love birds don't actually place all their eggs in one basket.

MinuteEarth tells us that there is, however, one species where true love is forever -- the Diplozoon Paradoxum.

"When two of these young flatworm find each other, they literally fuse together to form what looks like a single organism, and this adultry-free union lasts for their entire long and amourous lives, which they spend sucking blood from fish skills -- a truly romantic attachment."