The Kiryus (Zero and Ichiru's parents)

They are Zero and Ichiru's parents and are also Vampire Hunters.

Character concept
Neither their faces nor names have been revealed. In the light novels, they are merely referred to as "Zero's mother or father."

Appearance
The father bears a striking resemblance to Zero and Ichiru in terms of hair and skin coloring. The mother has long blondish-brown hair tied in a low ponytail.

History
Both Kiryus are high-ranking Vampire Hunters and are the parents of Zero and Ichiru Kiryu. Despite loving both their sons dearly, the Kiryus felt that Ichiru's illness and lack of natural talent compared to Zero would prevent him from becoming a Hunter. For this reason, they focused more of their time on developing Zero's skills as a Hunter, giving Ichiru the impression they generally preferred Zero over Ichiru. The resentment this fostered in Ichiru would have tragic consequences later on and lead to the destruction of their family. These events would be set in motion the night the Kiryus were assigned to kill an ex-human vampire who they'd been told had fallen to Level E. Unfortunately, the Kiryus were lied to and had been used as pawns by Rido Kuran to kill the ex-human vampire who had become his fiancée, Shizuka Hio's lover. Shizuka's grief over the death of her lover would drive her to insanity, and later, to revenge. With the assistance of Ichiru, who had become captivated by her, Shizuka killed both Kiryus, bit Zero, and took Ichiru away.

Trivia

 * Zero's mother is the first female Hunter we see.