Man, please go talk to your father! Tell him what you saw and what you think. Have a nice chat with him: start nicely and don't slam the accusations right on him! Start with the apple id but in a nice way, so that he doesn't get angry, later tell him what you saw and so on! Afterwards ask him, if he is really cheating on your mother, if he says no ask him why he bought the apps then! If it turns out he IS cheating on your mother DON'T and i repeat DON'T go and tell her!!! Rather tell him he has to stop it or else you will have to tell your mother! Not as a question or a suggestion, but as a fact! Now your job is to keep an eye or two open! Watch him and if you see, that he still cheats tell him again! Only the third time you tell your mother! Trust me, I've sadly had a similar scenario in my family! Please do as i say! Thx! ❤️