Xiao Ai walked down the street with her sister Xiao Hui. Suddenly Xiao Ai said to Xiao Hui, "Oh, my nephew Xiao Gang is working in the bakery in front of us. Let's buy some bread. " But Xiao Hui said "I do not have a nephew called Xiao Gang. ". According to this, Xiao Hui should be Xiaogang's. ['Aunt.', 'Wife.', 'Mom.', "Father's sister."]