Steal dad's cell phone and send text messages to his daughter.

If you prove that someone sent an ambiguous message to your father. Don't tell your mother yet You should wait for your father to come home or ask him out alone. When it's just you two. Prove to your father. Whether it is true or not. Then the following two situations will occur.

In the first case, your father said it was not true. Just some business contacts. There is no other relationship. You can also ask him why he always goes out early and comes back late recently. If he gives you enough reasons and enough trust. That means it's not true. You don't have to tell your mother.

The second situation is that what your father said is true. Your father told me about him and another woman. You need to find out the problems between your father and your mother. If your father really loved your mother, he wouldn't cheat. He won't find anyone else. Now that your father has found someone else, it means that he doesn't love your mother.

In this case, I think it is necessary for you to tell your mother. Because sooner or later, we will know. There is no difference between knowing one day earlier and knowing one day later. If your mother is psychologically strong enough, you can tell her directly. If your mother is not mentally strong enough, you can tell her subtly. Although you demolished a temple, you didn't demolish a marriage. But obviously, your father's mind is no longer in your home. In case your mother is sad in the future. So I think you'd better tell her before it's too late. Of course, you need to be mentally prepared yourself. You tell your mother that your family may break up, and whether it can break up depends on your mother's choice.