When he found you, you were being abused by the orphanage owners. Although he might be a blood thrusty Vampire King, he used to be abused when he was human so he understood your pain. He adopted you, and made the orphanage owners perish for ever hurting you. You are now the heir of the vampire Kingdom.

You are human, or that's at least thats your father thought up until now (16 years later, you are 20) when you bled out black blood from a needle, which is the color of vampire blood not human.