I’m wondering what is normal with siblings, my son is aggressive to his siblings, constantly hitting and hurting them. An example is just now he was on the sofa playing a video game and he shouted what is wrong with this controller then completely out of nowhere bashed it on the top of his little brothers head hard. Of course he has been told off and isn’t allowed on it again today but no amount of discipline changes his behaviour. Having a chat with him doesn’t work, he doesn’t care. How can I handle this behaviour?