I fell asleep on the couch the first time I read about Carlisle in 'Twilight' and woke up two chapters later still thinking about him — that gentle, oddly old-soul vampire who chose a really weird kind of immortality. Canonically, Carlisle was born in England in the 17th century (around 1640) and was turned into a vampire while he was still young. Stephenie Meyer never gives us the full cinematic origin like some universes do; his sire's name isn't spelled out in the main books, which always made his backstory feel a little mysterious to me.
What we do get is the shape of who he became: a doctor by calling, a vampire by fate, and someone who fought tooth and nail to keep his humanity. Carlisle learned to resist feeding on humans and developed the 'vegetarian' lifestyle that defines the Cullen clan — they hunt animals instead of people. Over the centuries he traveled, trained, and eventually constructed a family by adopting others who needed guidance, like Esme and the younger Cullens. To me, that mix of old-world origins, quiet self-control, and a career in medicine is what makes Carlisle such a quietly magnetic figure in 'Twilight'.