Does the subject want to ask, "Is the black diamond Xiao Yu's brother?" Yes Black diamond and Xiaoyu are both characters in the cartoon Pleasant Goat and Big Big Wolf. Black diamond is Xiaoyu's brother. In the animation, there are many pictures of Xiaoyu's brother and sister getting along in Black Diamond's mind, which actually shows that Black Diamond is Xiaoyu's brother. Someone erased brother Xiaoyu's memory and turned him into a robot.