Sumiko Sumimura

Sumimura Sumiko is the wife of Shuji, daughter of Shigemori Sumimura, and the mother of Masamori, Yoshimori, and Toshimori. She is also a kekkaishi, but is not a Legitimate Successor. Sumiko has a logical, confusing, somewhat cold nature. She is often called a bad (or at least non-present) mother by others, a claim that always infuriates Masamori and Yoshimori. Sumiko tends to make most people uncomfortable, often on purpose.

(Source: Kekkaishi Wikia)