where should it be?

Let your brother undastand that, when he refuse to listen and respect elders, when he grows up to adulthood, respect cannot be given to him by younger ones.

Alot of children especially when they become teenagers seem to not respect their parents. Eventually though a teenager that has been taught correctly when they were younger will learn about giving and getting respect. Children eventually always turn back to the things they have been taught when they were very young. Believe me when he does realize what he is doing to your mom he will be very sorry and hopefully it won't be too late for her to forgive him. Good luck in trying to help your mother all you can do right now is be there for her when she needs somebody.

Young people nowadays are rebellious without reason. There must be something going on with him that's why he's like that. Could be friend's influence, society, the internet, etc. They even refuse to talk and tell about what's going on with them. Does he have a very close friend that you could reach out to and ask how your brother is outside your home? Sometimes, this young people feel they are misunderstood and not loved by their family. They're insecure and try to find ways to get happiness from other sources.

Respect is not something you can teach like a lesson in a school but is something you gain and choose on yourself base on how you treat others. In other words, no matter how hard you teach your brother about respect, in the end, it's still he's choice if he'll apply it or not. But don't lose hope, nothing will happen if you don't do something therefore it is not too late to change him the way you want him to be. Remember that a person can't change as soon as possible but remember that the lesson they learned will remain for them forever. It's up to you on what way you'll do to help your brother gain back the respect for others.