Rules Werewolves Have To Follow In Every Twilight Movie

Another controversial aspect of the werewolves in "Twilight" is the matter of imprinting. The exact purpose of imprinting is a bit muddled, but it generally serves as a way for shape-shifters in the Quileute tribe to find their soulmates — though it doesn't have to be a romantic soulmate. Jacob explained it in his own words, saying, "It's not like love at first sight, really. It's more like... gravity moves. When you see her, suddenly it's not the earth holding you here anymore. She does. And nothing matters more than her."

When a werewolf imprints, they become extremely protective of the imprinted-upon person, and will do anything to make them happy, whether that be romantically or in a sibling way. Though Jacob imprints on Bella and Edward's infant daughter Renesmee, he's adamant that it's in a brotherly or even paternal way, and he acts as a sort of bodyguard for Renesmee throughout the rest of the series. 

Another important rule of imprinting is that once a werewolf imprints, the other pack members can't harm the imprintee, no matter what. This comes in handy since the climax of the werewolf-vampire battle is due to Renesmee's birth. However, once Jacob imprints on her, the fighting stops immediately.