One night, Alucard met a girl named Sonia Belmont while traveling through a remote mountain village. He was on his way to defeat his father but decided to stay and formed a bond with her. He would later decide to finish his resolve but encountered Sonia once more inside of Dracula's Castle. She had decided to challenge the Count as well, after her grandfather had been slain by his minions. He challenged her to a duel in order to test who of them was the most cunning warrior. To his surprise, he found himself defeated. Afterward Alucard sealed himself away.
After ending Dracula's evil reign, Sonia gave birth to their son, who would later continue the fate of the Belmont Clan and Alucard's bloodline.
↑Akumajō Dracula: Dark Night Prelude Official Guide: ドラキュラ伯爵と人間の女性との間に生まれたバンパイア・ハーフ. 父探しの旅の途中でソニアと出中会う. "Half vampire born from Count Dracula and a human woman. Meets Sonia in the middle of a journey to find his father."
↑IGA: 漆黒たる前奏曲は、ドラキュラの世界観をまったく無視して作られた作品だったため、私がプロデューサになった時に、正しい歴史からはずしました。あくまで同じ世界観をつかった別の世界の物語と考えてくだされば良いかと存じます。 Translation: Because Castlevania Legends was a work that completely ignored Castlevania's look, when I became producer, I removed it from the proper history. I think it would be best to think of it as a story from a different world that used the same look.