Dear Steve and Shirley, I'm thirty seven years old and my sister is forty five. I'm staying with her and her live in boyfriend of seven years. I've been having sex with her boyfriend and it started after I was here only a week. For years, the sexual tension has been strong between me and her boyfriend, but I was married at the time. A few years ago. She mentioned it, but she wasn't mad. I wondered if it was on her mind when I moved in with him, but it's like she doesn't care at all....................................................