Alice was held in a mental asylum because of her ability to have visions. There she was the favorite of a vampire who worked in the building. James, a hunter vampire, took the challenge of hunting her. Once it was clear to him that James was after her, he, the vampire who worked in the asylum, freed Alice and changed her before James could kill her. James killed the other vampire instead. She had no memory of these events and was left to find her own way.
At some point Alice saw Jasper in a vision. He had already been changed into a vampire by someone creating a vampire army. He was searching for someone and Alice provided him with what he was looking for. They found each other in 1948 and by 1950 they had found Carlisle with more help from her visions. They have been members of the family ever since.
Alice and Jasper have been officially married, but unlike Rosalie and Emmett, once was enough.
In 1935, Emmett was out hunting in the mountains of Tennessee when he was attacked by a bear. He very nearly died, but Rosalie found him and brought him to Carlisle to be saved. Emmett describes the event as being saved by an angel who brought him to God. Once the pain of the change had passed, Rosalie and Carlisle explained the situation to him, and to their surprise, the whole vampire issue didn’t disturb him. In his own words: “But if Carlisle and Rosalie, my angel, were vampires, how bad could it be?" He had trouble with the rules at first and has tasted human blood on several occasions.
Hope I helped!
Really cool character profiles: http://www.twilightlexiconblog.com/?page_id=6
· 1 decade ago