Hi there. I can understand that this can be very distressing. I would like to tell you that it's very common for children to enact what they see on the TV or in real life like enacting their teachers or elders. This behaviour is present in almost everyone. Right now Behaviour Therapy can help eliminate the issues your brother might be showing.
Next Steps
You can consult a psychotherapist or me for the same.
Health Tips
Please refrain from losing your temper over the kid