Torsten.

In medieval legend, a cambion is the half-human offspring of the union between a human male and a succubus, or of an incubus and a human female.
The cambion is a still birth that shows no sign of life outside of being alive, meaning that the child has, for example, no pulse and no breath. This continues until the child is about seven years old, where it becomes increasingly difficult to differentiate one from a human. A cambion is usually devilishly cunning, and angelically beautiful, able to persuade even the most strong-hearted individual to do his or her bidding. Most cambions have evil tendencies due to their demon parent.

Stolen information from Wikipedia.

Torsten had a human mother and an Incubus for a father. His mother passed away a few short years after Torsten was born, and the strange, beautiful little boy was taken in by his uncle, Gottfrid. Torsten was always mischievous, constantly getting into trouble -- though he was never punished. He always talked his way out of the punishment.
The day he turned seven, December third, was the very first day his heart began to beat, and he took his very first breath. Gottfrid found it a miracle, and wished to celebrate, but the other villagers refused. Torsten was a freak of nature, not taking his first breaths until he was seven years of age, his heart never beating, his skin cold and lifeless. So Gottfrid took him out of the village for the day, hoping to cheer the slightly disappointed Torsten up, by giving him a day of fun, no matter how cold it was. When they returned, the village was in shambles, and corpses of all who rejected Torsten lie strewn on the ground, claw marks all around them. No one ever said a word about the strange child again.
Torsten has an unnaturally long lifespan, having lived through the hundreds of years and to this very day, never looking a day older than twenty-five, when he stopped aging. He holds those who are close to him dear, having given Gottfrid a proper, viking funeral. He is strong and smart, and protects those who he loves.