Dear Aurora,
I'm very sorry for hiding all the truth from you. Please, don't take it as I didn't care about you, or didn't love you. Your father and I agreed to hide the truth to protect you.
Your father was a vampire, an ancient one, who could have children, however, in modern vampires, this function isn't working. I'm not good at such details, your father never told me everything, only things I should know and tell you one day in case it would be needed. However, you were happy working as a police officer and till my last breath, I believed you don't need to know who you really are.
You're a dhampir, a rare creature as your father said, and your rarity is lying in the fact that you're alive. Mostly, human females weren't able to give the birth, but somehow I managed. However, some people didn't like the fact of you being alive, they considered everything new as a threat.