My story happened several years ago. Dad had just had a heart attack and they found several blockages. At this time, open heart surgery was fairly new and only a few hospitals performed the surgery. Dad had a friend that was on the staff at Cleveland Clinic and he arranged for the surgery to be handled there. My sister and I decided to travel to Cleveland to give mom some support.
My sister was in her late 20's and I was in my early 30's at this time. We were normal siblings that pretty much had little to do with each other as kids, but the older we got the more we did things together. Mandy had turned into a pretty good looker. Nice ass and great tits and she dressed to show them. She was living with a guy that we all liked and I had been divorced for about 15 months.
The trip started out fairly mundane. We talked about dad and memories of our teen years. We talked about people we dated in our teens and wondered what they were doing these days. I told my sister that I would like to look up the girl I dated in high school to see what she was doing. I confessed we were each other's "first" and was had sex as often as possible. Mandy informed me that she knew we were having sex and she had a place in the basement that she would hide and watch us. Needless to say, my face got red and all I could say was "I hope you enjoyed the show".
I changed the subject to her and her live in boyfriend. Damn that was the wrong subject. Mandy started to cry and said that they haven't had sex in months and she was so horny that she could fuck a door knob. Again, she made me blush.