Dear MIMsters: My Mum Tells Me Everything, Will I Betray Her if I Don’t Tell Her This Secret?

Will I betray my mum if I keep this secret away from her?

My step-dad is a wonderful father to his children and even me but he cheats. I don’t know the level on which he is right now but I know he still cheats.

Fast forward to a year ago, my sister told me she saw a document showing that my dad has a son from another woman who should be eight years old by now. She told me and asked what we should do.

I did not want to break this kind of news to mum. I knew one day this issue would crop up and I would not be able to face my mum if she asks me why I did not tell her. I told my uncle so he would handle it in a mature way.

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I want to keep quiet on this issue but I wonder how she would feel if she finds out I knew. Meanwhile mu mum tells me everything. How do I go about this as I really want to keep quiet? My dad has not told her and I believe that he has no intention of telling her. It’s eight years now.

My younger sister confronted him and he confirmed it was true. The three of us know and we are all quiet about it. Is this fair to my mum?