" vampires were born male, their female counterpart a human with a genetic difference. The human female mate was born with her soul combined with that of her vampire mate, a genetic mutation that meant that she had to call her mate to her, before he lost his life force. Female mates did not live beyond their thirtieth year unless they became bonded with their vampire. "

― J.S. Scott , Ethan's Mate (The Vampire Coalition, #1)