Quick recap, I saw her giving him a blow job and then saw some pics on her phone, that part is [here](https://www.reddit.com/r/gonewildstories/comments/5jta53/i_32m_cant_stop_thinking_about_my_26f_sister/).
This time though I actually saw them have sex. It was last night, at around 10 that I was at my inlaws place for new years. We are a huge family so we get together sometimes there, sometimes with other relatives, etc. But there we were and my sister was wearing this very cute and revealing thing, very short skirt with very high boots and a red tight shirt, she looked very good to be honest. So we’re there all of us, like maybe 25 people between relatives and in-laws, and around 10:30 or a quarter to 11 she gets a phone call and immediately I knew it was from my boss. I don’t know why but I knew, maybe it was the look on her face or how she was smiling when talking to him but I knew. So she let’s everyone know that she’s gonna leave, and says goodbye to everybody, and everybody’s telling her to stay and whatever but she says she’s going to her friend’s house, which of course I knew it was bullshit, I knew she was going to see him and have a really good new years getting fucked.