Yukibe was a child who looked like a mixture between Yukime and Nube, whom everyone assumed was caused by their union. His real origin, however, was solely based on Yukime's powers. Apparently, as a yuki-onna reaches maturity, she develops a power to create a snow-child who would play with her before flying off into the mountains, a way she brings winter to the world. Yukibe possessed the freezing power that Yukime has, and he caused a great deal of havoc before finally flying off, bringing snow to Doumori. Although this is Yukibe's only real appearance, Nube consistently is reminded of him whenever he imagines the idea of him and Yukime having a real child, giving him further disgust over the relationship between a human and a yuki-onna.
(Source: Wikipedia)