My sister May did this to me one time when I came home from a date complaining of suffering fron Blue Balls. My girlfriend was stroking my cock while I was fingering her.... when we heard her parent's car pulling into the driveway. Embarrassed by a towering hardon in my pants when her parents came through the front door, I left my girlfiend in a rush. My cock was still hard when I got home and May could not help but notice the tent in my pants. Mom and Dad were out with friends and when May asked about my discomfort, I tried to explain what happened at my gf's home without being too graphic about it. May smiled coyly and said, "Poor blue balls brother. Would you like me to finish what your girlfriend started?'