Over 300 years ago, when Carlisle realized that he'd become a vampire, he was horrified and tried to kill himself, but nothing worked. Refusing to feed off humans, he became weak, until he discovered that he could go on all-animal (no-human) diet.
He spent his time attending universities in Europe and met painters and other vampires in Italy. But Carlisle never fit in with the other vampires because he refused to drink human blood. Lonely, he eventually moved to America, where, in 1918 as a doctor, he met Edward, dying from influenza. He saved Edward, and thus began the Cullen family.
Edward admits to Bella that as a young vampire, he rebelled against Carlisle's no-human diet and took off on his own for a while:
"It took me only a few years to return to Carlisle and recommit to his vision. I thought I would be exempt from the…depression…that accompanies a conscience. Because I knew the thoughts of my prey, I could pass over the innocent and pursue only the evil. If I followed a murderer down a dark alley where he stalked a young girl – if I saved her, then surely I wasn't so terrible. […] But as time went on, I began to see the monster in my eyes. I couldn't escape the debt of so much human life taken, no matter how justified. And I went back to Carlisle and Esme." (16.80-82)
Edward shows Bella his bedroom, which is crammed full of CDs.
Alice and Jasper stop by. Alice says there's going to be storm tonight, so they're going to be playing baseball. She wants to know if Edward and Bella want to join, which they do.