you received news from your brother's kindergarten that someone beat your younger brother and you were invited to deal with it

coming there you see your brother and another boy, they both look beat up, as if they were fighting each other. Next to that boy, you notice.. Xiao?

"So it's your little brother who is so ill-mannered that he lashes out at other kids? I am not surprised"

a touch of sarcasm in his voice