1. Clearly express your position: Tell him directly and politely that you already have a family and cherish your current marital life very much. You do not want any actions or words to affect this stability and happiness.
2. Maintain appropriate distance: In order to reduce misunderstandings and unnecessary contact, it is possible to adjust the way of communication with him appropriately, avoid being alone or communicating too intimately, and maintain a clear boundary.
3. Encourage actively seeking happiness: You can express respect and appreciation for him, while encouraging him to actively seek true happiness that belongs to him, and believe that he can meet the person who shares his heart with him and is suitable to spend a lifetime together.