Amelia is an orphan. She was taken in and raised by Silas Des'Caina in 895. At the same time, he took in an elven girl named Alexia. Alexia was five at the time, and Amelia was four; neither of them had names, so names were given to them by Silas, who they both came to think of as their father. And more than any of the other children he took in, Alexia and Amelia considered each other sisters. Amelia has no memory of her real parents, though Silas speculated that they may have been explorers who found the Isle of Freedom by chance, and most likely died (or were killed) before they could return to the domain of humans. Whatever the case, he found Amelia one day, huddled together with Alexia, though the two were never able to explain how they came to meet. It is sometimes said that Des'Caina named her after Amelia Mysshroudedtery, because she had taken a chance in hiring him as a sorcerer for InterGang; however, this didn't happen until 902, so obviously that story is impossible. Another story holds that the InterGang capo took a chance on Des'Caina after having met his "daughter," who happened to have the same name as her. While this is a possibility, it isn't known whether there's any truth to it.
All of the children Silas had taken in over the years were originally referred to by the surname "Foundling," a common name which may be applied to any number of people who are not actually related, much like "Protestant." Eventually each of Des'Caina's Foundlings was allowed to choose his or her own name, though apparently either they were not allowed, or chose not to go by the name "Des'Caina." It's not known if there's any special reason Amelia chose the name "Sinmore," though "sin" being a subword meaning "transgression against God," the name does seem fitting for a vampyre.
Amelia was sired by Girarg Blackshirt in 912.