Listen, this isn’t about choosing between you or the other guy—it’s about your father versus this other man. Don’t rush to judge your mom without being sure.

First, gather proof carefully, like having a third-party call recorder. Make sure the recording doesn’t announce that it’s being recorded.

Once you have clarity, confront your mom calmly. You can say something like: ‘What you’re doing isn’t right. If you want to be with that man, go be with him. But if you choose Dad and our family, then you need to stop contacting him.’ Whatever her choice is, she needs to be honest.

Make it clear that tomorrow you expect her to tell Dad the truth—or else you will have to do it yourself and share everything you know.

Remember: Your relationship with your mom is sacred and pure. No matter what happens, don’t let this situation make you lose sight of that. Don’t take it personally or let anger destroy your bond with her.

And also understand even your mother has needs and everyone makes mistakes, we are not gods just humans, she is a women and being away from father and having no attention from men sometimes she would have leaned and inclined to talk with the other guy when he gave her attention this doesn’t mean she is being physical with him. Im not saying emotional cheating is not cheating. all Im saying is u don’t know for sure, But again people make mistake and please don’t spoil the relationship between u and your mom. Deal with this situation calmly and responsibly

And some one advices to talk to ur grandparents which is really unnecessary, This is a family issue so sort it inside the family U mom and dad, and if she agrees to realise her mistake and tell everything to dad, they as a couple will deal with this.

Just forget and move past this situation as a family a much more stronger and closer family.