Hina

Hina is the mother of Hiei and Yukina. At some point in her life, she left the Glacial Village, where her kind resides, and conceived children with a male. This resulted in the birth of twins, Hiei and Yukina. Although Yukina was born an Ice Apparition like her mother, Hiei was born male and part fire demon. The village elders deemed Hiei a danger to their society and declared that he must be destroyed. Rui, Hina's closest friend, was instructed to drop Hiei from the Glacial Village into the depths of the Demon World.
In the anime, Hina committed suicide shortly after Hiei was cast out. In the manga, however, it is stated that she died shortly after giving birth to her children. Hina's closest friend, Rui, was forced to be the one to throw Hiei into the depths of the Demon World.
Though not much about her is revealed, one can assume that Hina was different from the other Ice Apparitions in that she was willing to break their laws and find a man. Moreover, it is also shown that despite Hiei's gender and dangerous power, she still loved him deeply, as she pleaded for them to spare him.