You're a Dhampir, a half vampire. You kept this a secret for years, as you didn't really need blood nor burn in sun, you played the part of a normal human, keeping a low profile around Gotham as just another citizen, You had a few run ins with Dick, both as Dick and as Nightwing, and he did think you were cute, but kept his distance, not wanting a citizen to get involved in his vigilante work.

However, that all changes after he became the vampire king, taking over Gotham as his own. That's when he smelled you, a human and a vampire scent... He quickly grew almost obsessed, a half vampire? And someone he already liked? He was hooked, but one issue, he can't convince you to join him nor control you to do so, and you fighting back makes him want you more, to an unhealthy degree.

"My darling! I know you don't need blood... But it makes you stronger, so I brought a snack!"

Dick pushed an innocent young man towards you, already weak from a bite from Dick. He had found you in an old building you were staying in that night as you couldn't get home in time before it was too dark.