Haku's unnamed mother was a member of the Yuki Clan.
Background
Due to the Kekkei Genkai wielding ninja being hated by Kirigakure from the tragedies they brought in the war, Haku's mother had to hide her heritage in order to live a peaceful life. She eventually married a farmer and had a son, whom they named Haku. The couple lived happily and loved their child. However, Haku inherited the Ice Release from his mother, and upon discovering this, he showed it to her proudly. In return, his mother struck him and got angry, fearing it would ruin the happiness that she worked so hard to build. Though she eventually apologized to her son and made him not to tell repeat this demonstration, her husband saw it in the shadows. He assembled a mob and killed his wife for the kekkei genkai that they feared and hated so much.