My brother and his wife had split up and one weekend when he has visitation with them he brought them over to visit their grandmother and their uncle which is me. I was about 17 when this happened. My brother took off with my mom to go visit a sister of mine for a few hours. I took his daughters who were about 8 years old to go swimming since we had a neighborhood pool just across the street. We swam for a few hours and then went back to my place to change and have lunch.

Well the girls decided it would be funny to keep busting in on me while I changed. We didn't have doors that locked so I couldn't do anything about it. I was trying to change and kept covering myself. But the constant busting in (which was about every 20 seconds) wouldn't let me change. I covered myself each time but the whole thing was getting me hard. Heck I am just a teenager. Finally I stood up to put my underwear on and they came in through the adjoining bathroom door. I couldn't cover myself since my shorts were below my knees. I tried to pull them up and turn but they saw my now hard cock standing up. I yelled at them and told them I was going to tell their dad! One of them just said, "Wow uncle Bill you have a really big wacker!" With that they left the room and stopped bugging me.