My father cheated me. I want to send a text message to Xiao San to warn him. What should I send?

I don't think it's a good idea to give a warning, because that mistress may tell your father, so maybe your father will scold you and his heart will be biased towards mistress.

I think you should talk to your father sometime. I have a classmate. She's like you. Her father has a mistress, but she has an idea. She told her father this way: Dad, I already knew about your relationship with that woman, but I didn't tell my mother because I didn't want her to know. I just want to say one thing to you: Dad, I love you and your mother, and I love this family. I don't want to lose it.

After she finished, her father broke up with Xiao San. I think her method is very good. Maybe you can try it. I hope it can help you.