Jonathan was an original member of Eccarius' Les Enfents du Sang in New orleans, and held on to the group with Lili after their leader's death. For Jonathan, the group was a kind of a dream, a living death that he could enjoy with other people. He was a languid young man, who seemed to be devoid of the passions that motivated the rest of the group.
Rest assured, he was as committed to Les Enfects du Sang as anyone else. He regularly indulged in blood drinking, and allowed others to drink his blood. He put himself in danger for the group, getting his hand shot off by Tulip and going one-on-one with Cassidy in an attempt to get the vampire to change him. He did manage to cut off Cassidy's head, but failed in his ultimate goal.
He did not get to live forever. He died on his own sword in a cemetery. Tragic and romantic. He was probably secretly pleased.