Sister in law Fulfilled Her Cum Fantasy

Story: I am going about my day as usually but there's one thing that I just can't get out of my head. I suspect that my brother in law is cheating on my sister. I can't be sure until I have proof so I try to find a way to get it. I google ways to spy on somebody and, to my astonishment, I come across an app that allows you to see someone's messages. It takes me only a few scrolls to find his conversation with a person named WetSchoolGirl. I immediately figure that she must be some kind of a whore and it gets me so mad. It isn't the end of surprises though. It turns out that my brother in law has a thing for me and the girl has been roleplaying me. I can't believe my own eyes. This is madness! I continue reading and I can't help but to get turned on. I start touching myself and indulging into the chat. DANG IT! THAT'S SO INAPPROPRIATE! But he has been thinking about me? It couldn't get hotter! I finish myself and end up rethinking it all. A few days pass and there's no new messages between the two and even though it shouldn't, it gets me upset. I am struggling to choose between telling my sister and making her husband mine. I go through the app and apparently I can text my sister's husband pretending to be that WetSchoolGirl. I am taken aback when he acctually replies. I start to ask him questions about he's fantasy to see if he is serious about it and he couldn't be more serious. He even shares a pic of my panties that he stole. I am dissapointed in myself that it turns me on so badly but I touch myself to orgasm anyway. I want more and more. I give a challenge - he has to cover my panties in his cum and leave them on my bed for me to see. He is hesitant but agrees, unaware that it has been me that whole time. On the weekend, my husband and I are having a dinner party with my sister and her husband. When the men leave to do men stuff, I am chatting with my sister when "WetSchoolGirl" gets a message. It's a picture of my panties covered in my brother's in law cum laying on my bedsheets. I excuse myself, head to the bedroom and immediately grab the panties. I put them on and start masturbating. There's nothing stopping me right now, lust wins. I cum and leave the panties on. Later, when the dinner is over, my brother in law messages again: I think she has put on the panties! I act dumb but my pussy is throbbing. That's when I find out he wants to get me pregnant. A couple of days later, I catch him stroking his cock in my bathroom. I pretend it be mad: What do you think you're doing?! But at this point, there's no hiding anymore. We head to the bedroom and fuck. He takes me missionary and then I ride him. It's the best sex of my life. I scream loudly that this is what I want and he cums massively inside me. We reflect for a moment - our lives have forever changed.