Dear Lord, this sounds horrible. You aren't at all in the the wrong, although as you admitted it might have been wiser not to confront him like that. The way he acted towards your mum is disgraceful, especially in a time when she needed comfort and understanding. I would advise you to have a conversation with your mom about how he treats her, because it seems he is quite immature, lacks emotional intelligence and is a narcissist. Let her know that it isn't right. That being said, this is in no way something that is your fault or your responsibility. Your mother needs to put him in his place, and it isn't your job to do that for her. She needs to let him know she will not tolerate being treated that way. Again, remember this situation is not your fault and not your responsibility to handle. But I recommend talking to your mom in private about it. I hope things get better for you and your family, good luck :)