Vol.9 Ch.33 - The king is working for the evil angel who demanded they be in prison and executed in front of the entire kingdom in an effort to harvest their negative emotions for more power. The kids go berserk thinking their mother has been murdered and go on a rampage. The singing baby stops the rampage but they’re still three going wild.
I Became the Mother of the Strongest Demon Lord's 10 Children in Another World.