If my son-in-law contacts another girl, how can I talk to him?

Talk to him calmly and let him know that you don't know what he is doing, but give him a chance to correct himself. Tell him that it is understandable that a man is a little sloppy, but that doesn't mean he is right. To be a man, we must first learn the word responsibility, learn morality and keep the bottom line of being a man. Playing with other people's feelings is also being played by others and life. Believe that he is a fool, he is a wise man, and he knows what to do.