The surrounding environment has a great influence on people. People with environmental education have correct thoughts and behaviors. A bad environment will make people degenerate and decadent. The story of Meng Mu's Three Movements tells us that this is the truth. I think it's better to talk to him often than to discipline him strictly. If he says this, don't criticize you severely. Once you criticize him, he thinks you don't understand and he won't tell you anything in the future. You can tell him by innuendo that it's wrong, don't be too strict, and then tell him something. It is best to show him some practical things, such as how some criminals will commit crimes in the end, and let him know that these things can't be done. In terms of sex, as a brother, you should also tell your younger brother some physiological knowledge, so that he can understand what is going on, which will not be good for his development, and will also affect his later sex life and so on. I hope my answer can help you!