Mom and Dad got home as expected (after Charlene had left), and were pleased to see that Sis, Charlene, and I had apparently behaved ourselves.
From then until Sis and Charlene went off to schools, the three of us continued to get considerable pleasure with each other in varying combinations — sometimes it was me and Charlene, or me and Sis; but I was fine with it when Charlene and Sis wanted to have their fun together, too. That I never did anything to interfere or interrupt them was appreciated; enough so that they were perfectly willing to provide the entertainment/stimulation to get ME going.
Nobody in our school ever did find out what the "real deal" was with Charlene, even though she ultimately became as much a part of everyday school activities as everyone else.
That was all several years ago, and I've graduated college and got my own wife and kids (one of each) now. Just as my parents did for me, I've done the best I can to bring them up with open minds, well-rounded personalities, and good characters — and made sure they understood that the could come to.