Just as Esther Dawn witnessed a part of his lover's past that he was never told about. He had no idea that Mayonaka Yoru was also watching his childhood memories. Esther Dawn's childhood can be described as happy. He is the son of a loving mother, a strict but loving father, and upcoming younger siblings.
The only thing he didn't know about his mother and father was their identities. Thana Daybreak, Esther Dawn's mother, is a noble-ranking vampire. She is only one of the blood race's high-ranking vampires. The Daybreak Clan also had ties to the Progenitor of Blood, who transformed the only Duke-ranked Vampire Lord. This is why her lineage has a pureblood component, as does Duke Luther D'Arcy's.
But because human marriage to other races is illegal, the Dawn Family can only flee. Furthermore, Luciel Dawn is a Cardinal, which means he holds a high position and power in the Templar Temple. They would never allow such a person to be with someone of the opposite race.