I came home to find my “in a relationship” older brother in a compromising position with our older sister.

So this happened about a month ago.<br><br>I’m a 22 female and I have an older brother (26) and older sister (29) My brother and I are living with our parents because of work and college issues. My sister lives with her husband (33) in a city about 2 hours away. I’ll call the husband P.<br><br>The incident occurred on a weekend when my sister came to visit our family. My brother was in a long distance relationship (1 year) with a woman that he met online, but he never told us where she was from. I’ll call the woman M. He told us that M’s job required her to travel around the world a lot, so that’s why they were in a long distance relationship. He showed us photos of him and M, but we weren’t sure if the photos were photoshopped. <br><br>On this particular weekend, my sister arrived after dinner, so she spent the night. All of us went to bed and the following morning, my sister helped me make breakfast. After breakfast, my sister said that she was going upstairs to look for my brother because he was supposed to drive her to the mall to buy her some gift certificates. I didn’t see my brother at breakfast, so I assumed that he was either in his room sleeping or in the backyard doing some gardening. <br><br>After my sister went upstairs, I heard her scream and I went up to check on her. I saw that the door to my brother’s room was opened, and when I looked inside, I saw my brother having sex with my sister. I was so confused and I didn’t know what to do. My sister looked at me and she looked ashamed. My brother also looked at me and he looked like someone had caught him. I left the room and went back downstairs. <br><br>I didn’t tell my parents what happened. I didn’t want to ruin the weekend for them. I called P and told him what I saw and he wasn’t surprised. He told me that a few months ago, he caught my brother and my sister having sex at his house, when he came home from work early. He said that he was tired of covering for my brother and that it was better if I told my parents.<br><br>I didn’t tell my parents when they came home. I was afraid of how they would react. My brother and my sister were quiet for the rest of the weekend and they didn’t leave their rooms. After my sister left, I noticed that my brother was receiving a lot of calls and messages. I assumed that it was M calling him and I felt sorry for him.<br><br>Two weeks later, my brother and his girlfriend M came to visit us. My parents were surprised to see M and they were asking her a lot of questions. M seemed nice and she appeared to be in love with my brother. My parents were so happy that they were together and they kept thanking M for making my brother happy. <br><br>The three of us were in the living room when my brother excused himself and took my sister’s car keys from her purse. I didn’t understand what was happening, but I assumed that he was going to buy something from her and she had left her keys with my parents. He went outside and forgot his phone. M and I were talking when my brother’s phone rang. <br><br>I looked at the phone and the name “Sis” popped up. I saw the name and the phone number and I recognized the phone number as my sister’s number. I answered the phone and it was my sister. She was asking my brother if he was okay and if our parents believed their story. I told her that I was the one on the phone and she was shocked. I asked her what was happening. She told me that she and my brother were in a relationship and they didn’t want our parents to know yet. <br><br>I was confused. I asked her what was going to happen to her husband and she told me that she was going to leave him for my brother. I told her that my brother was in a relationship with M and that she was there with us. She told me that M was my brother’s friend and that my brother lied to our parents that M was his girlfriend. She asked me who M really was and I told her that M was my brother’s friend. <br><br>I didn’t know if M was my brother’s friend or girlfriend. So I told my brother and M that I was going out with friends and I took them to a park. I told them that I had something important to tell them and my brother left to buy us snacks. <br><br>When my brother left, I told M that I had seen my brother and my sister having sex. M didn’t appear shocked. Instead, she told me that my brother and my sister were in a relationship. I asked her why she was with my brother then. She told me that my brother would spend the weekend with her and then go to my sister’s house. She said that my brother would help her spend her money and my brother would sleep with her friends. <br><br>I asked her what she got out of the relationship and she told me that she took him on trips and paid him a lot of money. She said that she was in love with my brother, but she knew that she could never be with him. She asked me if I could help her keep my parents from knowing about my brother and my sister. I told her that I would help her and all of us agreed to tell a lie. <br><br>My lie was that I was the one who came up with the idea of M visiting us and that my brother and M were together. She even spent some of her money on me and my friends. I didn’t hear from my sister again until last week. She called me and she told me that she left P. She said that my brother and her were going to move in together. <br><br>Last night, I saw my brother and M in a club, taking shots and dancing. I dancer near them, but they didn’t see me. I left after an hour and I went home. <br><br>I feel bad for my parents. How can I tell them?