1. Let me know that this behavior is inappropriate. Explain to him that this is an act of disrespect for others' privacy and personal space, and let him know that it will bring bad feelings to his sister and family.
2. Help the younger brother to establish correct values. You can help him establish correct values by discussing the importance of respecting others and letting him know other appropriate behaviors.
3. Let the younger brother bear the consequences. If he continues this behavior, he needs to understand that it will lead to some bad consequences, such as being punished by the school or losing some rights.
4. Make rules with your family. This can help the younger brother understand the mutual respect and concern among family members and strengthen the mutual supervision among family members.
5. Seek professional help. If your brother's behavior persists, you can consider seeking professional help, such as a child psychologist or an education consultant.
In a word, educating my younger brother needs patience and understanding, so that he can understand the influence of his actions on others and himself, and help him find the right way to express himself and get along with others.