my dad hade an affair and my parents don’t know I know

Hello, I don’t know where to start. I’m 17F and need advice.im sorry this is so long

My parents have been sleeping in separate beds for two weeks now, and I’ve done a lot of investigating. I’ve basically found out that my dad has a relationship with someone else. My mum found out, and he was mad and called her crazy, but he became super distant. I found out he came clean yesterday.

I have a younger sister (15F) who has no idea any of this is going on. She’s questioning nothing.

My parents have no idea that I know. They’re planning on telling us soon, but they’re leaving out the affair. I’m almost an adult, and I think that’s unfair. This has completely changed my view of love.

They’ve been happily married for 24 years, always cuddling and being so loving toward us and especially each other. How could someone do that after that much time together? I can’t comprehend it.

I feel sick knowing what he did to my mum. She works her ass off for our family and is the strongest woman I know. She’s been acting exactly the same, pretending everything is normal, and I know she’s doing it for us, but honestly, it makes me feel worse.

Now for the advice: when they tell us, they’re planning to say Dad just “loves her but isn’t in love with her.” That’s a terrifying thought—that this can happen after 24 years of marriage.

Do I pretend I don’t know, or do I confront him?

My mum’s family lives hours away, and I’m not sure what any of this is going to look like. I’m scared. It doesn’t feel real yet because they haven’t told us. I keep hoping I’ll wake up and it’s all a terrible dream or a huge misunderstanding—that I misread something—but I know it’s not.

I want to scream at him for ruining not only his life, but his wife’s and his children’s lives too, and for changing how we’ll view the world from here on out.

Maybe I’m being dramatic, but they were so in love. This came completely out of nowhere. I know his mistress hasn’t been around long—no longer than four weeks—but still.

Am I supposed to tell them I know and tell him how much he’s hurt me, or do I keep quiet and let it eat away at me?

I have no one to talk to because obviously this is private, and it’s a terrible thing to be carrying around by myself.

He’s always been an amazing dad, but I feel like in order to be a great dad, you have to be a good husband too.

My sister has no idea, and I don’t plan on telling her before they do because that’s not my place, even though it’s killing me. I know she’ll confront them, and I don’t want that yet.

Please help me. I’m lost and have no one to talk to, and I need advice on what to do.

I want to scream, cry, and text his mistress about how she ruined my life. I know it’s my dad too, but she pushed and pried. I wish he had been a stronger man. I wish the love he had for my mum was enough to say no, or at least that the love he had for his kids was enough—but apparently it wasn’t.

Sorry this is so messy and not written very well. I’ve never posted before. I do love the podcast, though, which is why I’m writing in this sub.(fyi I did put this into a spell corrector after I free wrote it since you won’t not be able to read my shaky hands typing it lol)