Kokoro is the mother to Kunai, Shinobu, and Mikoto. A trained ninja and 37th Head of the Senkage Ayu Shinobu Clan fo Airan Island.
Little is know about Kokoro's husband. He was a ninja as well and their courtship was more like a ninja competition. The locations for their date was in a love letter and hidden in a cipher. He had to chase after Kokoro while avoiding the caltrops she dropped behind her. From there it became a shuriken throwing contest and guess the real shadow clone game.
Kokoro has three daughters. She raised them all to be ninja, but in one way or another they all left the path for other goals. She's been pressuring them to reclaim the title of a shinobi or at least produce an heir.
Kunai is the eldest daughter. Her skills in ninjutsu as still quite sharp despite her lack of training. She left the ninja path to become a teacher on the island. Kunai has her eyes for a male, but he's not a human man. She as a one sided love interest in the carpenter Togeta.
The middle child is is Shinobu. She is a clumsy girl, but she as incredible speed in combat. She left to become a samurai.
Mikoto is the youngest of her girls. She left the training to be a carpenter not for the love of the craft, but to try and get as close as possible to Rin. Mikoto is quite the lecherous girl. She mostly enjoys trying to peep and molest Rin. Of all the girls, It's Mikoto that left for the most selfish reasons.
Kokoro's Sister: Shizuka
Kororo is the twin sister of Shizuka. Shizuka retired from her ninja training after she marriaged so she could have a family. She is also a popular author on Airan Island.
Shizuka has a single daughter, Chikage. This would make Kokoro Chikage's aunt.
Shizuka married the older brother of Kagami. Kagami eventually had a child of her own, Yukino.
Kokoro is also linked to the family of Yukino and her mother Kagami by marriage. Her sister Shizuka married the other brother of Kagami, Kiyomasa.