Rebecca Groveton was hunted one night. A pureblood attacked her as she was walking home with a male friend. The man was killed, his neck snapped quickly so the vampire could take his time and enjoy the woman. She tried to fight back, but he quickly overpowered her. The vampire discovered that after only one swallow he was sated of his bloodlust. He was 'full', and no longer felt the need to feed. He felt refreshed and strong, more so than after any other feeding where the victim was fully drained.
After only a little more than an hour, Rebecca had her full complement of blood back in her system. She had somehow remade what she'd lost within her own body.
He let her go, and had his familiars watch her for the next few days, but she did not turn. She was immune to vampire infection. When he next felt the hunger he took her again, for he craved the exhilarating feeling her blood gave him.
This time he did not release her, nor did he stop at just feeding from her. Rebecca was attractive for a human, and she had a fiery personality which the vampire found engaging. It was not uncommon for vampires to turn those whom they desired, but Rebecca could not be turned. As a human she suffered his desires, but he was not unkind to her. He allowed no other vampires to take either blood or sex from her.
As a pureblood immortal, he had been around for centuries, and knew what it was to be a gentleman. Contrary to some conceptions concerning cold-hearted killers, vampires can love, though usually only their own kind because they regard humans as inferior. Rebecca was no mewling maiden, she had spirit.
He made sure she was comfortable, and she grew used to her life. She'd not have admitted it to anyone, least of all herself, but she even grew to like her dark protector.
He was killed by jealous vampires while he was protecting her. He wouldn't share her, and he paid with his life.
Humans can have human children. Pureblood vampires can have pureblood vampire children.
Only once before had a human woman given birth to something with vampire blood – Blade – but at the time he had not yet made himself known to the vampires. No one suspected that Rebecca could have been pregnant when she ran away, but she was. While in hiding, she had a daughter.
Caitlyn was not a vampire. She never grew fangs, never had the thirst, was never allergic to sunlight, garlic or silver. But nor was she completely human. She had her mother's trait of recovering quickly from bloodloss, even faster than Rebecca could. She'd been bitten once, and did not turn. She didn't regenerate quite as quickly as vampires, but she was still a fast healer. She could see well in the dark, and was strong, and agile, though she had trained herself to be like that during her childhood. She did have superior strength and speed to normal humans, and plenty of endurance, but she never made this obvious unless she had to fight, in which case there were no unwanted witnesses by the end.
When Caitlyn met her first vampire, she found that she could sense his presence near her, feel his hunger. She was still young and inexperienced, so he got her. The vampire didn't get to tell anyone about it, because she killed him while he was still foolishly distracted by what her blood was making him feel. After that encounter she used her senses as a warning, and she continued enhancing her other skills. No vampire had bitten her since.
Caitlyn had power, she could feel it running through her veins. She learned how to heal others and bring life to the dying. She could sense both life and death. She learned how to ignite things like flesh, so that she could destroy a vampire even if there was no silver handy.
To balance this destructive power, Caitlyn learned how to grow things, a peaceful and calming exercise that proved to have a practical purpose. Rebecca's little garden started overflowing with vegetables. They needed to eat, after all. Caitlyn also grew lots of garlic, she even made it grow all over the outside walls of the house, a smelly but effective vampire repellent. An oak tree was grown strong and tall next to the house in a matter of hours, and Caitlyn refined her control by forming twirls and knots in the limbs. She made a comfortable, moss-covered bench out of one of the thick roots.
To make a long story a little bit shorter, Caitlyn came out of hiding and started hunting vampires for a living when she was old enough. She found Kevin one night, having been drawn to the sense of hungry vamps. He was heavily outnumbered and she evened the odds for him. She'd been with his unit of the Nightstalkers ever since.