History
Born in 1843 in Texas, Jasper was turned twenty years later by a vampire named Maria. She wanted him for his combat skills - he'd risen quickly through the ranks of the Confederate army - and for some time, he fought with her, training newborn vampires to fight and killing them when their usefulness had expired.
When he tired of this, he escaped Maria's clutches, fleeing with two old friends. For a time, he wandered with them, but he soon realized that he was unable to eat people, as he could feel their emotions before death and it was overwhelming.
He wandered on his own for a bit until he met Alice in a diner - she had foreseen their meeting - and he traveled then with her until they met the Cullens.
Ever since, they have been together, and part of Carlisle's family.
Personality
Jasper is a fairly private person, and therefore quiet. He can come off as cold at times - most times, really - though in truth he is a very compassionate person. He wants others to feel at ease around him, and when necessary he will use his vampiric gift of emotion manipulation to shift the emotional field.
Skills
Jasper's vampiric ability allows him to feel and manipulate the emotions of others.