I'm so very sorry you've had to find this out. It must be devastating seeing as you now probably feel piggy in the middle. Obviously you have to do whatever you feel is best. But if you put yourself in your mums shoes would you want to know? How would you feel if you knew your daughter knew but didn't say anything? 

Personally if it was me I'd have to confront my dad and tell him I knew and ask him to tell your mum (his wife) and give him a period of time to do that, say within a fortnight and then say you'll have no choice but to tell her yourself. 

Sadly I have had to do this and tell a friend. We met for lunch and I told her in a coffee shop so it was in a neutral space. Of course she was devastated but thanked me for being a friend. I felt absolutely terrible watching her relationship break up but i knew I couldn't hide it from her. 

I hope you find the strength to do what's right for you and your family right now. 

I'm so very sorry you've had to find this out. It must be devastating seeing as you now probably feel piggy in the middle. Obviously you have to do whatever you feel is best. But if you put yourself in your mums shoes would you want to know? How would you feel if you knew your daughter knew but didn't say anything? 

Personally if it was me I'd have to confront my dad and tell him I knew and ask him to tell your mum (his wife) and give him a period of time to do that, say within a fortnight and then say you'll have no choice but to tell her yourself. 

Sadly I have had to do this and tell a friend. We met for lunch and I told her in a coffee shop so it was in a neutral space. Of course she was devastated but thanked me for being a friend. I felt absolutely terrible watching her relationship break up but i knew I couldn't hide it from her. 

I hope you find the strength to do what's right for you and your family right now.