Opportunities come every so often that when one gets the chance it is often taken for the regret of the unknown outcome would be worse than taking action. Even if you've lived for several hundred years certain opportunities come once even for a vampire.
The Cullen's family, the secret resident vampires of the small town in Washington state, called Forks. They had one such opportunity fall into their laps. Vampires are the natural enemies of werewolves, besides the long standing animosity between the groups there is little under standing of how the other lives. Would it even be possible to develop relationships that did not consist of hate, disgust, and distrust. Carlisle Cullen wondered about the possibilities of truly getting to learn about other race. Because of the animosity that was taught to the werewolves at a young age it was essentially impossible to ever form such an understanding or relationship.
The treaty that maintains the uneasy peace between the local vampires and werewolves has lasted for over one hundred years. The rules put forth by the treaty keeps the two groups very isolated from one another, using distance as the key to prevent war. The young Quileute are taught to stay far away from the bloodsuckers. For a pacifist vampires like Carlisle Cullen and his family, it is impossible to develop an understanding relationship without animosity after a Quileute child has been taught to mistrust them.
The fateful opportunity that could give Cullen clan a chance to develop such a relationship with a Quileute child happened from the aftermath of tragedy. In such a situation is it worth breaking a treaty for a chance to obtain an understanding that would otherwise be unobtainable? Such a debate went through the minds of Carlisle and Esme Cullen as they chose to ignore the complaints of their adopted children and take the Quileute child.