If you see that you are getting a double chin or a double chin, it can have various causes. It may be because your skin is slackening, which is part of aging. Heredity also plays a role. If you are overweight, you are more likely to suffer from a double chin, but also if you lose a lot of weight and your skin remains slack.
Note that if you are overweight, these exercises alone will not suffice. You will therefore have to pay attention to your diet and train the rest of your body to see results.