This happened about 3 weeks ago before school year started. We are a very typical American Family. 3 kids, 2 grown and John the last a senior in high school. Let me begin to say he is a very good student, quiet, nice friends, and has had a very nice girlfriend for just over a year. I work about 30 minutes from our home and had forgotten that a contactor was to come over to estimate some work. I had to leave work early and meet him. Upon arriving home I noticed my sons girlfriends car parked on the street, not even a mere thought as they are avid cyclists and must have gone for ride. I went into our home and immediately noticed a door that is usually left open, was closed. This area goes to our finished basement where there is another door usually kept open, but was also closed. I could hear some music playing down there and figured John and his girlfriend were playing some video games since we have a big screen TV. Curious I went down the stairway,called his name but no response. Again curious I slowly opened the door and was utterly shocked at what was going on. John was fucking her like a bronco, my usually quiet, studious son was having the time of his life. I know he is a teen and probally horny, but the both of them were going at it with such raw lust that I am still dumbfounded. His girlfriend is also shy, (or so I thought) but she was rocking like a horse while my son pounded her from every which way, then he was giving oral like he has been doing this for many years, tounges flickering, her telling him she wanted more and more until I closed the door went upstairs and out of the house in shock? I still have not told my wife and of course have not mentioned this to my son who would be utterly embarrased. Should I talk to him? He is so seemingly shy that his raw sex actions being seen my me is just amazing, and I must admit, very erotic for me, keeping very personal thoughts to myself. I am actually hoping to see them again...oddly enough as time passes I am turned on by viewing them, as the contrast from everyday life was so erotic, so different and certainly so unexpected.What I find fascinating is that when we see them together or having dinner they are very polite, somewhat quiet, we even know her family. So the visual of seeing these two go at it like wild animals is still abit shocking? Have said nothing yet, am still keeping things to myself. As an adult father of a son I am also somewhat proud of him as I NEVER even gave his sex life or interest much thought until this happened. Normal or not this must happen daily in families and in this day and age maybe it is normal??