I had a similar, surreal experience many years ago with my first wife and her divorced Mother after a Saturday evening of drinking......My then wife was getting a little 'amourous' and was kissing my neck on the sofa, and began to stroke my thigh over my jeans, and I could not help getting stiffer......I felt a little nervous and strange when I noticed her Mum gazing at the outline along my thigh, and giving me a cheeky little smile....